X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfunc.pod;h=92dbc2a135ad25d191859205a4a7dd5a167c427d;hb=20408e3ccf502b6ce4033d8203710405ec9ef8f6;hp=b55e1b1ba655f88bc6d3dc350bb1fcf930e41547;hpb=f827b0a6c8a4efd53c50a16b098f59ac04fd670d;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index b55e1b1..92dbc2a 100644
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -1,3 +1,4 @@
+
 =head1 NAME
 
 perlfunc - Perl builtin functions
@@ -35,11 +36,11 @@ operator or unary operator, and precedence does matter.  And whitespace
 between the function and left parenthesis doesn't count--so you need to
 be careful sometimes:
 
-    print 1+2+3;	# Prints 6.
-    print(1+2) + 3;	# Prints 3.
-    print (1+2)+3;	# Also prints 3!
-    print +(1+2)+3;	# Prints 6.
-    print ((1+2)+3);	# Prints 6.
+    print 1+2+4;	# Prints 7.
+    print(1+2) + 4;	# Prints 3.
+    print (1+2)+4;	# Also prints 3!
+    print +(1+2)+4;	# Prints 7.
+    print ((1+2)+4);	# Prints 7.
 
 If you run Perl with the B<-w> switch it can warn you about this.  For
 example, the third line above produces:
@@ -48,7 +49,7 @@ example, the third line above produces:
     Useless use of integer addition in void context at - line 1.
 
 For functions that can be used in either a scalar or list context,
-non-abortive failure is generally indicated in a scalar context by
+nonabortive failure is generally indicated in a scalar context by
 returning the undefined value, and in a list context by returning the
 null list.
 
@@ -79,117 +80,120 @@ than one place.
 
 =item Functions for SCALARs or strings
 
-chomp, chop, chr, crypt, hex, index, lc, lcfirst, length,
-oct, ord, pack, q/STRING/, qq/STRING/, reverse, rindex,
-sprintf, substr, tr///, uc, ucfirst, y///
+C<chomp>, C<chop>, C<chr>, C<crypt>, C<hex>, C<index>, C<lc>, C<lcfirst>,
+C<length>, C<oct>, C<ord>, C<pack>, C<q>/STRING/, C<qq>/STRING/, C<reverse>,
+C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>, C<y>///
 
 =item Regular expressions and pattern matching
 
-m//, pos, quotemeta, s///, split, study
+C<m>//, C<pos>, C<quotemeta>, C<s>///, C<split>, C<study>
 
 =item Numeric functions
 
-abs, atan2, cos, exp, hex, int, log, oct, rand, sin, sqrt,
-srand
+C<abs>, C<atan2>, C<cos>, C<exp>, C<hex>, C<int>, C<log>, C<oct>, C<rand>,
+C<sin>, C<sqrt>, C<srand>
 
 =item Functions for real @ARRAYs
 
-pop, push, shift, splice, unshift
+C<pop>, C<push>, C<shift>, C<splice>, C<unshift>
 
 =item Functions for list data
 
-grep, join, map, qw/STRING/, reverse, sort, unpack
+C<grep>, C<join>, C<map>, C<qw>/STRING/, C<reverse>, C<sort>, C<unpack>
 
 =item Functions for real %HASHes
 
-delete, each, exists, keys, values
+C<delete>, C<each>, C<exists>, C<keys>, C<values>
 
 =item Input and output functions
 
-binmode, close, closedir, dbmclose, dbmopen, die, eof,
-fileno, flock, format, getc, print, printf, read, readdir,
-rewinddir, seek, seekdir, select, syscall, sysread,
-syswrite, tell, telldir, truncate, warn, write
+C<binmode>, C<close>, C<closedir>, C<dbmclose>, C<dbmopen>, C<die>, C<eof>,
+C<fileno>, C<flock>, C<format>, C<getc>, C<print>, C<printf>, C<read>,
+C<readdir>, C<rewinddir>, C<seek>, C<seekdir>, C<select>, C<syscall>,
+C<sysread>, C<sysseek>, C<syswrite>, C<tell>, C<telldir>, C<truncate>,
+C<warn>, C<write>
 
 =item Functions for fixed length data or records
 
-pack, read, syscall, sysread, syswrite, unpack, vec
+C<pack>, C<read>, C<syscall>, C<sysread>, C<syswrite>, C<unpack>, C<vec>
 
 =item Functions for filehandles, files, or directories
 
-I<-X>, chdir, chmod, chown, chroot, fcntl, glob, ioctl, link,
-lstat, mkdir, open, opendir, readlink, rename, rmdir,
-stat, symlink, umask, unlink, utime
+C<-I<X>>, C<chdir>, C<chmod>, C<chown>, C<chroot>, C<fcntl>, C<glob>,
+C<ioctl>, C<link>, C<lstat>, C<mkdir>, C<open>, C<opendir>, C<readlink>,
+C<rename>, C<rmdir>, C<stat>, C<symlink>, C<umask>, C<unlink>, C<utime>
 
 =item Keywords related to the control flow of your perl program
 
-caller, continue, die, do, dump, eval, exit, goto, last,
-next, redo, return, sub, wantarray
+C<caller>, C<continue>, C<die>, C<do>, C<dump>, C<eval>, C<exit>,
+C<goto>, C<last>, C<next>, C<redo>, C<return>, C<sub>, C<wantarray>
 
-=item Keywords related to scoping 
+=item Keywords related to scoping
 
-caller, import, local, my, package, use
+C<caller>, C<import>, C<local>, C<my>, C<package>, C<use>
 
 =item Miscellaneous functions
 
-defined, dump, eval, formline, local, my, reset, scalar,
-undef, wantarray
+C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<reset>,
+C<scalar>, C<undef>, C<wantarray>
 
 =item Functions for processes and process groups
 
-alarm, exec, fork, getpgrp, getppid, getpriority, kill,
-pipe, qx/STRING/, setpgrp, setpriority, sleep, system,
-times, wait, waitpid
+C<alarm>, C<exec>, C<fork>, C<getpgrp>, C<getppid>, C<getpriority>, C<kill>,
+C<pipe>, C<qx>/STRING/, C<setpgrp>, C<setpriority>, C<sleep>, C<system>,
+C<times>, C<wait>, C<waitpid>
 
 =item Keywords related to perl modules
 
-do, import, no, package, require, use
+C<do>, C<import>, C<no>, C<package>, C<require>, C<use>
 
 =item Keywords related to classes and object-orientedness
 
-bless, dbmclose, dbmopen, package, ref, tie, tied, untie, use
+C<bless>, C<dbmclose>, C<dbmopen>, C<package>, C<ref>, C<tie>, C<tied>,
+C<untie>, C<use>
 
 =item Low-level socket functions
 
-accept, bind, connect, getpeername, getsockname,
-getsockopt, listen, recv, send, setsockopt, shutdown,
-socket, socketpair
+C<accept>, C<bind>, C<connect>, C<getpeername>, C<getsockname>,
+C<getsockopt>, C<listen>, C<recv>, C<send>, C<setsockopt>, C<shutdown>,
+C<socket>, C<socketpair>
 
 =item System V interprocess communication functions
 
-msgctl, msgget, msgrcv, msgsnd, semctl, semget, semop,
-shmctl, shmget, shmread, shmwrite
+C<msgctl>, C<msgget>, C<msgrcv>, C<msgsnd>, C<semctl>, C<semget>, C<semop>,
+C<shmctl>, C<shmget>, C<shmread>, C<shmwrite>
 
 =item Fetching user and group info
 
-endgrent, endhostent, endnetent, endpwent, getgrent,
-getgrgid, getgrnam, getlogin, getpwent, getpwnam,
-getpwuid, setgrent, setpwent
+C<endgrent>, C<endhostent>, C<endnetent>, C<endpwent>, C<getgrent>,
+C<getgrgid>, C<getgrnam>, C<getlogin>, C<getpwent>, C<getpwnam>,
+C<getpwuid>, C<setgrent>, C<setpwent>
 
 =item Fetching network info
 
-endprotoent, endservent, gethostbyaddr, gethostbyname,
-gethostent, getnetbyaddr, getnetbyname, getnetent,
-getprotobyname, getprotobynumber, getprotoent,
-getservbyname, getservbyport, getservent, sethostent,
-setnetent, setprotoent, setservent
+C<endprotoent>, C<endservent>, C<gethostbyaddr>, C<gethostbyname>,
+C<gethostent>, C<getnetbyaddr>, C<getnetbyname>, C<getnetent>,
+C<getprotobyname>, C<getprotobynumber>, C<getprotoent>,
+C<getservbyname>, C<getservbyport>, C<getservent>, C<sethostent>,
+C<setnetent>, C<setprotoent>, C<setservent>
 
 =item Time-related functions
 
-gmtime, localtime, time, times
+C<gmtime>, C<localtime>, C<time>, C<times>
 
 =item Functions new in perl5
 
-abs, bless, chomp, chr, exists, formline, glob, import, lc,
-lcfirst, map, my, no, prototype, qx, qw, readline, readpipe,
-ref, sub*, sysopen, tie, tied, uc, ucfirst, untie, use
+C<abs>, C<bless>, C<chomp>, C<chr>, C<exists>, C<formline>, C<glob>,
+C<import>, C<lc>, C<lcfirst>, C<map>, C<my>, C<no>, C<prototype>, C<qx>,
+C<qw>, C<readline>, C<readpipe>, C<ref>, C<sub*>, C<sysopen>, C<tie>,
+C<tied>, C<uc>, C<ucfirst>, C<untie>, C<use>
 
 * - C<sub> was a keyword in perl4, but in perl5 it is an
 operator which can be used in expressions.
 
 =item Functions obsoleted in perl5
 
-dbmclose, dbmopen
+C<dbmclose>, C<dbmopen>
 
 =back
 
@@ -197,11 +201,11 @@ dbmclose, dbmopen
 
 =over 8
 
-=item -X FILEHANDLE
+=item I<-X> FILEHANDLE
 
-=item -X EXPR
+=item I<-X> EXPR
 
-=item -X
+=item I<-X>
 
 A file test, where X is one of the letters listed below.  This unary
 operator takes one argument, either a filename or a filehandle, and
@@ -225,7 +229,7 @@ operator may be any of:
 
     -e	File exists.
     -z	File has zero size.
-    -s	File has non-zero size (returns size).
+    -s	File has nonzero size (returns size).
 
     -f	File is a plain file.
     -d	File is a directory.
@@ -275,7 +279,7 @@ are found, it's a C<-B> file, otherwise it's a C<-T> file.  Also, any file
 containing null in the first block is considered a binary file.  If C<-T>
 or C<-B> is used on a filehandle, the current stdio buffer is examined
 rather than the first block.  Both C<-T> and C<-B> return TRUE on a null
-file, or a file at EOF when testing a filehandle.  Because you have to 
+file, or a file at EOF when testing a filehandle.  Because you have to
 read a file to do the C<-T> test, on most occasions you want to use a C<-f>
 against the file first, as in C<next unless -f $file && -T $file>.
 
@@ -300,7 +304,7 @@ symbolic link, not the real file.)  Example:
 
 =item abs VALUE
 
-=item abs 
+=item abs
 
 Returns the absolute value of its argument.
 If VALUE is omitted, uses $_.
@@ -313,7 +317,7 @@ See example in L<perlipc/"Sockets: Client/Server Communication">.
 
 =item alarm SECONDS
 
-=item alarm 
+=item alarm
 
 Arranges to have a SIGALRM delivered to this process after the
 specified number of seconds have elapsed.  If SECONDS is not specified,
@@ -326,8 +330,8 @@ starting a new one.  The returned value is the amount of time remaining
 on the previous timer.
 
 For delays of finer granularity than one second, you may use Perl's
-syscall() interface to access setitimer(2) if your system supports it, 
-or else see L</select()> below.  It is not advised to intermix alarm() 
+syscall() interface to access setitimer(2) if your system supports it,
+or else see L</select()>.  It is usually a mistake to intermix alarm()
 and sleep() calls.
 
 If you want to use alarm() to time out a system call you need to use an
@@ -370,9 +374,9 @@ L<perlipc/"Sockets: Client/Server Communication">.
 Arranges for the file to be read or written in "binary" mode in operating
 systems that distinguish between binary and text files.  Files that are
 not in binary mode have CR LF sequences translated to LF on input and LF
-translated to CR LF on output.  Binmode has no effect under Unix; in DOS
+translated to CR LF on output.  Binmode has no effect under Unix; in MS-DOS
 and similarly archaic systems, it may be imperative--otherwise your
-DOS-damaged C library may mangle your file.  The key distinction between
+MS-DOS-damaged C library may mangle your file.  The key distinction between
 systems that need binmode and those that don't is their text file
 formats.  Systems like Unix and Plan9 that delimit lines with a single
 character, and that encode that character in C as '\n', do not need
@@ -406,21 +410,21 @@ With EXPR, it returns some extra information that the debugger uses to
 print a stack trace.  The value of EXPR indicates how many call frames
 to go back before the current one.
 
-    ($package, $filename, $line, $subroutine, 
+    ($package, $filename, $line, $subroutine,
      $hasargs, $wantarray, $evaltext, $is_require) = caller($i);
 
 Here $subroutine may be C<"(eval)"> if the frame is not a subroutine
-call, but C<L<eval>>.  In such a case additional elements $evaltext and
-$is_require are set: $is_require is true if the frame is created by
-C<L<require>> or C<L<use>> statement, $evaltext contains the text of
-C<L<eval EXPR>> statement.  In particular, for C<L<eval BLOCK>>
-statement $filename is C<"(eval)">, but $evaltext is undefined. (Note
-also that C<L<use>> statement creates a C<L<require>> frame inside
-an C<L<eval EXPR>>) frame.
+call, but an C<eval>.  In such a case additional elements $evaltext and
+$is_require are set: $is_require is true if the frame is created by a
+C<require> or C<use> statement, $evaltext contains the text of the
+C<eval EXPR> statement.  In particular, for a C<eval BLOCK> statement,
+$filename is C<"(eval)">, but $evaltext is undefined.  (Note also that
+each C<use> statement creates a C<require> frame inside an C<eval EXPR>)
+frame.
 
 Furthermore, when called from within the DB package, caller returns more
 detailed information: it sets the list variable @DB::args to be the
-arguments with which that subroutine was invoked.
+arguments with which the subroutine was invoked.
 
 =item chdir EXPR
 
@@ -434,7 +438,7 @@ Changes the permissions of a list of files.  The first element of the
 list must be the numerical mode, which should probably be an octal
 number, and which definitely should I<not> a string of octal digits:
 C<0644> is okay, C<'0644'> is not.  Returns the number of files
-successfully changed.  See also L<oct>, if all you have is a string.
+successfully changed.  See also L</oct>, if all you have is a string.
 
     $cnt = chmod 0755, 'foo', 'bar';
     chmod 0755, @executables;
@@ -448,7 +452,7 @@ successfully changed.  See also L<oct>, if all you have is a string.
 
 =item chomp
 
-This is a slightly safer version of chop (see below).  It removes any
+This is a slightly safer version of L</chop>.  It removes any
 line ending that corresponds to the current value of C<$/> (also known as
 $INPUT_RECORD_SEPARATOR in the C<English> module).  It returns the total
 number of characters removed from all its arguments.  It's often used to
@@ -509,7 +513,7 @@ Returns the number of files successfully changed.
     $cnt = chown $uid, $gid, 'foo', 'bar';
     chown $uid, $gid, @filenames;
 
-Here's an example that looks up non-numeric uids in the passwd file:
+Here's an example that looks up nonnumeric uids in the passwd file:
 
     print "User: ";
     chop($user = <STDIN>);
@@ -522,23 +526,23 @@ Here's an example that looks up non-numeric uids in the passwd file:
     @ary = <${pattern}>;	# expand filenames
     chown $uid, $gid, @ary;
 
-On most systems, you are not allowed to change the ownership of the 
+On most systems, you are not allowed to change the ownership of the
 file unless you're the superuser, although you should be able to change
 the group to any of your secondary groups.  On insecure systems, these
 restrictions may be relaxed, but this is not a portable assumption.
 
 =item chr NUMBER
 
-=item chr 
+=item chr
 
 Returns the character represented by that NUMBER in the character set.
-For example, C<chr(65)> is "A" in ASCII.  For the reverse, use L<ord>.
+For example, C<chr(65)> is "A" in ASCII.  For the reverse, use L</ord>.
 
 If NUMBER is omitted, uses $_.
 
 =item chroot FILENAME
 
-=item chroot 
+=item chroot
 
 This function works as the system call by the same name: it makes the
 named directory the new root directory for all further pathnames that
@@ -551,19 +555,30 @@ omitted, does chroot to $_.
 
 Closes the file or pipe associated with the file handle, returning TRUE
 only if stdio successfully flushes buffers and closes the system file
-descriptor.  You don't have to close FILEHANDLE if you are immediately
-going to do another open() on it, because open() will close it for you.  (See
+descriptor.
+
+You don't have to close FILEHANDLE if you are immediately going to do
+another open() on it, because open() will close it for you.  (See
 open().)  However, an explicit close on an input file resets the line
-counter ($.), while the implicit close done by open() does not.  Also,
-closing a pipe will wait for the process executing on the pipe to
-complete, in case you want to look at the output of the pipe
-afterwards.  Closing a pipe explicitly also puts the status value of
-the command into C<$?>.  Example:
+counter ($.), while the implicit close done by open() does not.
+
+If the file handle came from a piped open C<close> will additionally
+return FALSE if one of the other system calls involved fails or if the
+program exits with non-zero status.  (If the only problem was that the
+program exited non-zero $! will be set to 0.) Also, closing a pipe will
+wait for the process executing on the pipe to complete, in case you
+want to look at the output of the pipe afterwards.  Closing a pipe
+explicitly also puts the exit status value of the command into C<$?>.
+Example:
 
-    open(OUTPUT, '|sort >foo');	# pipe to sort
+    open(OUTPUT, '|sort >foo')  # pipe to sort
+        or die "Can't start sort: $!";
     ...				# print stuff to output
-    close OUTPUT;		# wait for sort to finish
-    open(INPUT, 'foo');		# get sort's results
+    close OUTPUT		# wait for sort to finish
+        or warn $! ? "Error closing sort pipe: $!"
+                   : "Exit status $? from sort";
+    open(INPUT, 'foo')		# get sort's results
+        or die "Can't open 'foo' for input: $!";
 
 FILEHANDLE may be an expression whose value gives the real filehandle name.
 
@@ -607,9 +622,9 @@ the password file for lousy passwords, amongst other things.  Only the
 guys wearing white hats should do this.
 
 Note that crypt is intended to be a one-way function, much like breaking
-eggs to make an omelette. Thus, there is no (known) corresponding
-decrypt function, so this function isn't all that useful for
-cryptography. (For that, see your nearby CPAN mirror.)
+eggs to make an omelette.  There is no (known) corresponding decrypt
+function.  As a result, this function isn't all that useful for
+cryptography.  (For that, see your nearby CPAN mirror.)
 
 Here's an example that makes sure that whoever runs this program knows
 their own password:
@@ -627,9 +642,9 @@ their own password:
 	die "Sorry...\n";
     } else {
 	print "ok\n";
-    } 
+    }
 
-Of course, typing in your own password to whomever asks you 
+Of course, typing in your own password to whoever asks you
 for it is unwise.
 
 =item dbmclose HASH
@@ -675,7 +690,7 @@ rich implementation.
 
 =item defined EXPR
 
-=item defined 
+=item defined
 
 Returns a Boolean value telling whether EXPR has a value other than
 the undefined value C<undef>.  If EXPR is not present, C<$_> will be
@@ -697,7 +712,7 @@ is not guaranteed to produce intuitive results, and should probably be
 avoided.
 
 When used on a hash element, it tells you whether the value is defined,
-not whether the key exists in the hash.  Use L<exists> for the latter
+not whether the key exists in the hash.  Use L</exists> for the latter
 purpose.
 
 Examples:
@@ -706,8 +721,6 @@ Examples:
     print "$val\n" while defined($val = pop(@ary));
     die "Can't readlink $sym: $!"
 	unless defined($value = readlink $sym);
-    eval '@foo = ()' if defined(@foo);
-    die "No XYZ package defined" unless defined %_XYZ;
     sub foo { defined &$bar ? &$bar(@_) : die "No bar"; }
     $debugging = 0 unless defined $debugging;
 
@@ -740,10 +753,10 @@ them as not defined anymore, but you shoudln't do that unless you don't
 plan to use them again, because it saves time when you load them up
 again to have memory already ready to be filled.
 
-This counter-intuitive behaviour of defined() on aggregates may be
+This counterintuitive behaviour of defined() on aggregates may be
 changed, fixed, or broken in a future release of Perl.
 
-See also L<undef>, L<exists>, L<ref>.
+See also L</undef>, L</exists>, L</ref>.
 
 =item delete EXPR
 
@@ -775,7 +788,7 @@ hash element lookup or hash slice:
 
 Outside of an eval(), prints the value of LIST to C<STDERR> and exits with
 the current value of C<$!> (errno).  If C<$!> is 0, exits with the value of
-C<($? E<gt>E<gt> 8)> (back-tick `command` status).  If C<($? E<gt>E<gt> 8)>
+C<($? E<gt>E<gt> 8)> (backtick `command` status).  If C<($? E<gt>E<gt> 8)>
 is 0, exits with 255.  Inside an eval(), the error message is stuffed into
 C<$@>, and the eval() is terminated with the undefined value; this makes
 die() the way to raise an exception.
@@ -783,7 +796,7 @@ die() the way to raise an exception.
 Equivalent examples:
 
     die "Can't cd to spool: $!\n" unless chdir '/usr/spool/news';
-    chdir '/usr/spool/news' or die "Can't cd to spool: $!\n" 
+    chdir '/usr/spool/news' or die "Can't cd to spool: $!\n"
 
 If the value of EXPR does not end in a newline, the current script line
 number and input line number (if any) are also printed, and a newline
@@ -801,11 +814,28 @@ produce, respectively
 
 See also exit() and warn().
 
+If LIST is empty and $@ already contains a value (typically from a
+previous eval) that value is reused after appending "\t...propagated".
+This is useful for propagating exceptions:
+
+    eval { ... };
+    die unless $@ =~ /Expected exception/;
+
+If $@ is empty then the string "Died" is used.
+
 You can arrange for a callback to be called just before the die() does
 its deed, by setting the C<$SIG{__DIE__}> hook.  The associated handler
 will be called with the error text and can change the error message, if
-it sees fit, by calling die() again.  See L<perlvar> for details on
-setting C<%SIG> entries, and eval() for some examples.
+it sees fit, by calling die() again.  See L<perlvar/$SIG{expr}> for details on
+setting C<%SIG> entries, and L<"eval BLOCK"> for some examples.
+
+Note that the C<$SIG{__DIE__}> hook is called even inside eval()ed
+blocks/strings.  If one wants the hook to do nothing in such
+situations, put
+
+	die @_ if $^S;
+
+as the first line of the handler (see L<perlvar/$^S>).
 
 =item do BLOCK
 
@@ -828,13 +858,15 @@ from a Perl subroutine library.
 
 is just like
 
-    eval `cat stat.pl`;
+    scalar eval `cat stat.pl`;
 
 except that it's more efficient, more concise, keeps track of the
 current filename for error messages, and searches all the B<-I>
 libraries if the file isn't in the current directory (see also the @INC
-array in L<perlvar/Predefined Names>).  It's the same, however, in that it does
-re-parse the file every time you call it, so you probably don't want to
+array in L<perlvar/Predefined Names>).  It is also different in how
+code evaluated with C<do FILENAME> doesn't see lexicals in the enclosing
+scope like C<eval STRING> does.  It's the same, however, in that it does
+reparse the file every time you call it, so you probably don't want to
 do this inside a loop.
 
 Note that inclusion of library modules is better done with the
@@ -940,28 +972,44 @@ I<EACH> file in a while (E<lt>E<gt>) loop.  Examples:
     }
 
 Practical hint: you almost never need to use C<eof> in Perl, because the
-input operators return undef when they run out of data.  
+input operators return undef when they run out of data.
 
 =item eval EXPR
 
 =item eval BLOCK
 
-EXPR is parsed and executed as if it were a little Perl program.  It
-is executed in the context of the current Perl program, so that any
+In the first form, the return value of EXPR is parsed and executed as if it
+were a little Perl program.  The value of the expression (which is itself
+determined within a scalar context) is first parsed, and if there are no
+errors, executed in the context of the current Perl program, so that any
 variable settings or subroutine and format definitions remain afterwards.
-The value returned is the value of the last expression evaluated, or a
-return statement may be used, just as with subroutines.  The last
-expression is evaluated in scalar or array context, depending on the
-context of the eval.
+Note that the value is parsed every time the eval executes.  If EXPR is
+omitted, evaluates C<$_>.  This form is typically used to delay parsing
+and subsequent execution of the text of EXPR until run time.
+
+In the second form, the code within the BLOCK is parsed only once--at the
+same time the code surrounding the eval itself was parsed--and executed
+within the context of the current Perl program.  This form is typically
+used to trap exceptions more efficiently than the first (see below), while
+also providing the benefit of checking the code within BLOCK at compile
+time.
+
+The final semicolon, if any, may be omitted from the value of EXPR or within
+the BLOCK.
+
+In both forms, the value returned is the value of the last expression
+evaluated inside the mini-program, or a return statement may be used, just
+as with subroutines.  The expression providing the return value is evaluated
+in void, scalar or array context, depending on the context of the eval itself.
+See L</wantarray> for more on how the evaluation context can be determined.
 
 If there is a syntax error or runtime error, or a die() statement is
 executed, an undefined value is returned by eval(), and C<$@> is set to the
 error message.  If there was no error, C<$@> is guaranteed to be a null
-string.  If EXPR is omitted, evaluates C<$_>.  The final semicolon, if
-any, may be omitted from the expression.  Beware that using eval()
-neither silences perl from printing warnings to STDERR, nor does it
-stuff the text of warning messages into C<$@>.  To do either of those,
-you have to use the C<$SIG{__WARN__}> facility.  See warn() and L<perlvar>.
+string.  Beware that using eval() neither silences perl from printing
+warnings to STDERR, nor does it stuff the text of warning messages into C<$@>.
+To do either of those, you have to use the C<$SIG{__WARN__}> facility.  See
+L</warn> and L<perlvar>.
 
 Note that, because eval() traps otherwise-fatal errors, it is useful for
 determining whether a particular feature (such as socket() or symlink())
@@ -973,7 +1021,7 @@ form to trap run-time errors without incurring the penalty of
 recompiling each time.  The error, if any, is still returned in C<$@>.
 Examples:
 
-    # make divide-by-zero non-fatal
+    # make divide-by-zero nonfatal
     eval { $answer = $a / $b; }; warn $@ if $@;
 
     # same thing, but less efficient
@@ -999,11 +1047,11 @@ die() again, which has the effect of changing their error messages:
     # __DIE__ hooks may modify error messages
     {
        local $SIG{'__DIE__'} = sub { (my $x = $_[0]) =~ s/foo/bar/g; die $x };
-       eval { die "foo foofs here" };
-       print $@ if $@;                # prints "bar barfs here"
+       eval { die "foo lives here" };
+       print $@ if $@;                # prints "bar lives here"
     }
 
-With an eval(), you should be especially careful to remember what's 
+With an eval(), you should be especially careful to remember what's
 being looked at when:
 
     eval $x;		# CASE 1
@@ -1022,25 +1070,29 @@ and 4 likewise behave in the same way: they run the code '$x', which
 does nothing but return the value of C<$x>.  (Case 4 is preferred for
 purely visual reasons, but it also has the advantage of compiling at
 compile-time instead of at run-time.)  Case 5 is a place where
-normally you I<WOULD> like to use double quotes, except that in that
+normally you I<WOULD> like to use double quotes, except that in this
 particular situation, you can just use symbolic references instead, as
 in case 6.
 
 =item exec LIST
 
-The exec() function executes a system command I<AND NEVER RETURNS>,
-unless the command does not exist and is executed directly instead of
-via C</bin/sh -c> (see below).  Use system() instead of exec() if you
-want it to return.
+=item exec PROGRAM LIST
+
+The exec() function executes a system command I<AND NEVER RETURNS> -
+use system() instead of exec() if you want it to return. It fails and
+returns FALSE only if the command does not exist I<and> it is executed
+directly instead of via your system's command shell (see below).
 
 If there is more than one argument in LIST, or if LIST is an array with
 more than one value, calls execvp(3) with the arguments in LIST.  If
 there is only one scalar argument, the argument is checked for shell
-metacharacters.  If there are any, the entire argument is passed to
-C</bin/sh -c> for parsing.  If there are none, the argument is split
-into words and passed directly to execvp(), which is more efficient.
-Note: exec() and system() do not flush your output buffer, so you may
-need to set C<$|> to avoid lost output.  Examples:
+metacharacters, and if there are any, the entire argument is passed to
+the system's command shell for parsing (this is C</bin/sh -c> on Unix
+platforms, but varies on other platforms).  If there are no shell
+metacharacters in the argument, it is split into words and passed
+directly to execvp(), which is more efficient.  Note: exec() and
+system() do not flush your output buffer, so you may need to set C<$|>
+to avoid lost output.  Examples:
 
     exec '/bin/echo', 'Your arguments are: ', @ARGV;
     exec "sort $outfile | uniq";
@@ -1049,7 +1101,7 @@ If you don't really want to execute the first argument, but want to lie
 to the program you are executing about its own name, you can specify
 the program you actually want to run as an "indirect object" (without a
 comma) in front of the LIST.  (This always forces interpretation of the
-LIST as a multi-valued list, even if there is only a single scalar in
+LIST as a multivalued list, even if there is only a single scalar in
 the list.)  Example:
 
     $shell = '/bin/csh';
@@ -1059,6 +1111,10 @@ or, more directly,
 
     exec {'/bin/csh'} '-sh';	# pretend it's a login shell
 
+When the arguments get executed via the system shell, results will
+be subject to its quirks and capabilities.  See L<perlop/"`STRING`">
+for details.
+
 =item exists EXPR
 
 Returns TRUE if the specified hash key exists in its hash array, even
@@ -1087,7 +1143,7 @@ are called before exit.)  Example:
     exit 0 if $ans =~ /^[Xx]/;
 
 See also die().  If EXPR is omitted, exits with 0 status.  The only
-univerally portable values for EXPR are 0 for success and 1 for error;
+universally portable values for EXPR are 0 for success and 1 for error;
 all other values are subject to unpredictable interpretation depending
 on the environment in which the Perl program is running.
 
@@ -1097,9 +1153,9 @@ which can be trapped by an eval().
 
 =item exp EXPR
 
-=item exp 
+=item exp
 
-Returns I<e> (the natural logarithm base) to the power of EXPR.  
+Returns I<e> (the natural logarithm base) to the power of EXPR.
 If EXPR is omitted, gives C<exp($_)>.
 
 =item fcntl FILEHANDLE,FUNCTION,SCALAR
@@ -1125,21 +1181,28 @@ value is taken as the name of the filehandle.
 =item flock FILEHANDLE,OPERATION
 
 Calls flock(2), or an emulation of it, on FILEHANDLE.  Returns TRUE for
-success, FALSE on failure.  Will produce a fatal error if used on a
-machine that doesn't implement flock(2), fcntl(2) locking, or lockf(3).
-flock() is Perl's portable file locking interface, although it will lock
-only entire files, not records.
+success, FALSE on failure.  Produces a fatal error if used on a machine
+that doesn't implement flock(2), fcntl(2) locking, or lockf(3).  flock()
+is Perl's portable file locking interface, although it locks only entire
+files, not records.
+
+On many platforms (including most versions or clones of Unix), locks
+established by flock() are B<merely advisory>.  This means that files
+locked with flock() may be modified by programs which do not also use
+flock().  Windows NT and OS/2, however, are among the platforms which
+supply mandatory locking.  See your local documentation for details.
 
 OPERATION is one of LOCK_SH, LOCK_EX, or LOCK_UN, possibly combined with
 LOCK_NB.  These constants are traditionally valued 1, 2, 8 and 4, but
-you can use the symbolic names if you pull them in with an explicit
-request to the Fcntl module.  The names can be requested as a group with
-the :flock tag (or they can be requested individually, of course).
-LOCK_SH requests a shared lock, LOCK_EX requests an exclusive lock, and
-LOCK_UN releases a previously requested lock.  If LOCK_NB is added to
-LOCK_SH or LOCK_EX then flock() will return immediately rather than
-blocking waiting for the lock (check the return status to see if you got
-it).
+you can use the symbolic names if import them from the Fcntl module,
+either individually, or as a group using the ':flock' tag.  LOCK_SH
+requests a shared lock, LOCK_EX requests an exclusive lock, and LOCK_UN
+releases a previously requested lock.  If LOCK_NB is added to LOCK_SH or
+LOCK_EX then flock() will return immediately rather than blocking
+waiting for the lock (check the return status to see if you got it).
+
+To avoid the possibility of mis-coordination, Perl flushes FILEHANDLE
+before (un)locking it.
 
 Note that the emulation built with lockf(3) doesn't provide shared
 locks, and it requires that FILEHANDLE be open with write intent.  These
@@ -1191,7 +1254,7 @@ zombies:
 
     $SIG{CHLD} = sub { wait };
 
-There's also the double-fork trick (error checking on 
+There's also the double-fork trick (error checking on
 fork() returns omitted);
 
     unless ($pid = fork) {
@@ -1219,7 +1282,7 @@ you're done.  You should reopen those to /dev/null if it's any issue.
 Declare a picture format with use by the write() function.  For
 example:
 
-    format Something = 
+    format Something =
 	Test: @<<<<<<<< @||||| @>>>>>
 	      $str,     $%,    '$' . int($num)
     .
@@ -1232,7 +1295,7 @@ example:
 See L<perlform> for many details and examples.
 
 
-=item formline PICTURE, LIST
+=item formline PICTURE,LIST
 
 This is an internal function used by C<format>s, though you may call it
 too.  It formats (see L<perlform>) a list of values according to the
@@ -1264,7 +1327,7 @@ single-characters, however.  For that, try something more like:
 	system "stty cbreak </dev/tty >/dev/tty 2>&1";
     }
     else {
-	system "stty", '-icanon', 'eol', "\001"; 
+	system "stty", '-icanon', 'eol', "\001";
     }
 
     $key = getc(STDIN);
@@ -1277,18 +1340,18 @@ single-characters, however.  For that, try something more like:
     }
     print "\n";
 
-Determination of whether $BSD_STYLE should be set 
-is left as an exercise to the reader.  
+Determination of whether $BSD_STYLE should be set
+is left as an exercise to the reader.
 
 The POSIX::getattr() function can do this more portably on systems
 alleging POSIX compliance.
 See also the C<Term::ReadKey> module from your nearest CPAN site;
-details on CPAN can be found on L<perlmod/CPAN>.  
+details on CPAN can be found on L<perlmod/CPAN>.
 
 =item getlogin
 
 Returns the current login from F</etc/utmp>, if any.  If null, use
-getpwuid().  
+getpwuid().
 
     $login = getlogin || getpwuid($<) || "Kilroy";
 
@@ -1438,33 +1501,35 @@ Returns the socket option requested, or undefined if there is an error.
 
 =item glob
 
-Returns the value of EXPR with filename expansions such as a shell
-would do.  This is the internal function implementing the <*.c>
-operator, except it's easier to use.  If EXPR is omitted, $_ is used.
+Returns the value of EXPR with filename expansions such as a shell would
+do.  This is the internal function implementing the C<E<lt>*.cE<gt>>
+operator, but you can use it directly.  If EXPR is omitted, $_ is used.
+The C<E<lt>*.cE<gt>> operator is discussed in more detail in
+L<perlop/"I/O Operators">.
 
 =item gmtime EXPR
 
 Converts a time as returned by the time function to a 9-element array
-with the time localized for the standard Greenwich time zone.  
+with the time localized for the standard Greenwich time zone.
 Typically used as follows:
 
-
+    #  0    1    2     3     4    5     6     7     8
     ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
 					    gmtime(time);
 
 All array elements are numeric, and come straight out of a struct tm.
 In particular this means that $mon has the range 0..11 and $wday has
-the range 0..6.  Also, $year is the number of years since 1900, I<not>
-simply the last two digits of the year.
+the range 0..6 with sunday as day 0.  Also, $year is the number of
+years since 1900, I<not> simply the last two digits of the year.
 
 If EXPR is omitted, does C<gmtime(time())>.
 
-In a scalar context, prints out the ctime(3) value:
+In a scalar context, returns the ctime(3) value:
 
     $now_string = gmtime;  # e.g., "Thu Oct 13 04:54:34 1994"
 
-Also see the F<timegm.pl> library, and the strftime(3) function available
-via the POSIX module.
+Also see the timegm() function provided by the Time::Local module,
+and the strftime(3) function available via the POSIX module.
 
 =item goto LABEL
 
@@ -1500,7 +1565,7 @@ will be able to tell that this routine was called first.
 
 =item grep EXPR,LIST
 
-This is similar in spirit to, but not the same as, L<grep(1)>
+This is similar in spirit to, but not the same as, grep(1)
 and its relatives.  In particular, it is not limited to using
 regular expressions.
 
@@ -1519,27 +1584,30 @@ Note that, because $_ is a reference into the list value, it can be used
 to modify the elements of the array.  While this is useful and
 supported, it can cause bizarre results if the LIST is not a named
 array.  Similarly, grep returns aliases into the original list,
-much like the way that L<foreach>'s index variable aliases the list
+much like the way that L<Foreach Loops>'s index variable aliases the list
 elements.  That is, modifying an element of a list returned by grep
+(for example, in a C<foreach>, C<map> or another C<grep>)
 actually modifies the element in the original list.
 
+See also L</map> for an array composed of the results of the BLOCK or EXPR.
+
 =item hex EXPR
 
-=item hex 
+=item hex
 
-Interprets EXPR as a hex string and returns the corresponding 
+Interprets EXPR as a hex string and returns the corresponding
 value.  (To convert strings that might start with either 0 or 0x
-see L<oct>.)  If EXPR is omitted, uses $_.
+see L</oct>.)  If EXPR is omitted, uses $_.
 
     print hex '0xAf'; # prints '175'
     print hex 'aF';   # same
 
 =item import
 
-There is no built-in import() function.  It is merely an ordinary
+There is no builtin import() function.  It is merely an ordinary
 method (subroutine) defined (or inherited) by modules that wish to export
 names to another module.  The use() function calls the import() method
-for the package used.  See also L</use>, L<perlmod>, and L<Exporter>.
+for the package used.  See also L</use()>, L<perlmod>, and L<Exporter>.
 
 =item index STR,SUBSTR,POSITION
 
@@ -1553,7 +1621,7 @@ one less than the base, ordinarily -1.
 
 =item int EXPR
 
-=item int 
+=item int
 
 Returns the integer portion of EXPR.  If EXPR is omitted, uses $_.
 
@@ -1567,7 +1635,7 @@ first to get the correct function definitions.  If F<ioctl.ph> doesn't
 exist or doesn't have the correct definitions you'll have to roll your
 own, based on your C header files such as F<E<lt>sys/ioctl.hE<gt>>.
 (There is a Perl script called B<h2ph> that comes with the Perl kit which
-may help you in this, but it's non-trivial.)  SCALAR will be read and/or
+may help you in this, but it's nontrivial.)  SCALAR will be read and/or
 written depending on the FUNCTION--a pointer to the string value of SCALAR
 will be passed as the third argument of the actual ioctl call.  (If SCALAR
 has no string value but does have a numeric value, that value will be
@@ -1604,7 +1672,7 @@ system:
 
 =item join EXPR,LIST
 
-Joins the separate strings of LIST or ARRAY into a single string with
+Joins the separate strings of LIST into a single string with
 fields separated by the value of EXPR, and returns the string.
 Example:
 
@@ -1634,7 +1702,7 @@ or how about sorted by key:
 	print $key, '=', $ENV{$key}, "\n";
     }
 
-To sort an array by value, you'll need to use a C<sort{}> function.
+To sort an array by value, you'll need to use a C<sort> function.
 Here's a descending numeric sort of a hash by its values:
 
     foreach $key (sort { $hash{$b} <=> $hash{$a} } keys %hash)) {
@@ -1657,8 +1725,8 @@ as trying has no effect).
 
 =item kill LIST
 
-Sends a signal to a list of processes.  The first element of 
-the list must be the signal to send.  Returns the number of 
+Sends a signal to a list of processes.  The first element of
+the list must be the signal to send.  Returns the number of
 processes successfully signaled.
 
     $cnt = kill 1, $child1, $child2;
@@ -1686,17 +1754,17 @@ C<continue> block, if any, is not executed:
 
 =item lc EXPR
 
-=item lc 
+=item lc
 
 Returns an lowercased version of EXPR.  This is the internal function
-implementing the \L escape in double-quoted strings.  
+implementing the \L escape in double-quoted strings.
 Respects current LC_CTYPE locale if C<use locale> in force.  See L<perllocale>.
 
 If EXPR is omitted, uses $_.
 
 =item lcfirst EXPR
 
-=item lcfirst 
+=item lcfirst
 
 Returns the value of EXPR with the first character lowercased.  This is
 the internal function implementing the \l escape in double-quoted strings.
@@ -1706,7 +1774,7 @@ If EXPR is omitted, uses $_.
 
 =item length EXPR
 
-=item length 
+=item length
 
 Returns the length in characters of the value of EXPR.  If EXPR is
 omitted, returns length of $_.
@@ -1726,7 +1794,7 @@ it succeeded, FALSE otherwise.  See example in L<perlipc/"Sockets: Client/Server
 A local modifies the listed variables to be local to the enclosing block,
 subroutine, C<eval{}>, or C<do>.  If more than one value is listed, the
 list must be placed in parentheses.  See L<perlsub/"Temporary Values via
-local()"> for details.
+local()"> for details, including issues with tied arrays and hashes.
 
 But you really probably want to be using my() instead, because local() isn't
 what most people think of as "local").  See L<perlsub/"Private Variables
@@ -1738,24 +1806,37 @@ Converts a time as returned by the time function to a 9-element array
 with the time analyzed for the local time zone.  Typically used as
 follows:
 
+    #  0    1    2     3     4    5     6     7     8
     ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
 						localtime(time);
 
 All array elements are numeric, and come straight out of a struct tm.
 In particular this means that $mon has the range 0..11 and $wday has
-the range 0..6 and $year is year-1900, that is, $year is 123 in year
-2023.  If EXPR is omitted, uses the current time ("localtime(time)").
+the range 0..6 with sunday as day 0.  Also, $year is the number of
+years since 1900, that is, $year is 123 in year 2023.
+
+If EXPR is omitted, uses the current time (C<localtime(time)>).
 
 In a scalar context, returns the ctime(3) value:
 
     $now_string = localtime;  # e.g., "Thu Oct 13 04:54:34 1994"
 
-Also see the Time::Local module, and the strftime(3) function available
-via the POSIX module.
+This scalar value is B<not> locale dependent, see L<perllocale>, but
+instead a Perl builtin.  Also see the Time::Local module, and the
+strftime(3) and mktime(3) function available via the POSIX module.  To
+get somewhat similar but locale dependent date strings, set up your
+locale environment variables appropriately (please see L<perllocale>)
+and try for example
+
+	use POSIX qw(strftime)
+	$now_string = strftime "%a %b %e %H:%M:%S %Y", localtime;
+
+Note that the C<%a> and C<%b>, the short forms of the day of the week
+and the month of the year, may not necessarily be three characters wide.
 
 =item log EXPR
 
-=item log 
+=item log
 
 Returns logarithm (base I<e>) of EXPR.  If EXPR is omitted, returns log
 of $_.
@@ -1764,7 +1845,7 @@ of $_.
 
 =item lstat EXPR
 
-=item lstat 
+=item lstat
 
 Does the same thing as the stat() function, but stats a symbolic link
 instead of the file the symbolic link points to.  If symbolic links are
@@ -1798,6 +1879,12 @@ is just a funny way to write
 	$hash{getkey($_)} = $_;
     }
 
+Note that, because $_ is a reference into the list value, it can be used
+to modify the elements of the array.  While this is useful and
+supported, it can cause bizarre results if the LIST is not a named
+array.  See also L</grep> for an array composed of those items of the 
+original list for which the BLOCK or EXPR evaluates to true.
+
 =item mkdir FILENAME,MODE
 
 Creates the directory specified by FILENAME, with permissions specified
@@ -1861,7 +1948,7 @@ See the "use" function, which "no" is the opposite of.
 
 =item oct EXPR
 
-=item oct 
+=item oct
 
 Interprets EXPR as an octal string and returns the corresponding
 value.  (If EXPR happens to start off with 0x, interprets it as
@@ -1906,9 +1993,9 @@ L<IPC::Open2>, L<IPC::Open3>, and L<perlipc/"Bidirectional Communication">
 for alternatives.)
 
 Opening '-' opens STDIN and opening 'E<gt>-' opens STDOUT.  Open returns
-non-zero upon success, the undefined value otherwise.  If the open
+nonzero upon success, the undefined value otherwise.  If the open
 involved a pipe, the return value happens to be the pid of the
-subprocess.  
+subprocess.
 
 If you're unfortunate enough to be running Perl on a system that
 distinguishes between text files and binary files (modern operating
@@ -1918,6 +2005,14 @@ and those that don't is their text file formats.  Systems like Unix and
 Plan9 that delimit lines with a single character, and that encode that
 character in C as '\n', do not need C<binmode>.  The rest need it.
 
+When opening a file, it's usually a bad idea to continue normal execution
+if the request failed, so C<open> is frequently used in connection with
+C<die>. Even if C<die> won't do what you want (say, in a CGI script,
+where you want to make a nicely formatted error message (but there are
+modules which can help with that problem)) you should always check
+the return value from opening a file. The infrequent exception is when
+working with an unopened filehandle is actually what you want to do.
+
 Examples:
 
     $ARTICLE = 100;
@@ -1925,12 +2020,16 @@ Examples:
     while (<ARTICLE>) {...
 
     open(LOG, '>>/usr/spool/news/twitlog'); # (log is reserved)
+    # if the open fails, output is discarded
 
-    open(DBASE, '+<dbase.mine');	    # open for update
+    open(DBASE, '+<dbase.mine')		    # open for update
+	or die "Can't open 'dbase.mine' for update: $!";
 
-    open(ARTICLE, "caesar <$article |");    # decrypt article
+    open(ARTICLE, "caesar <$article |")     # decrypt article
+	or die "Can't start caesar: $!";
 
-    open(EXTRACT, "|sort >/tmp/Tmp$$");     # $$ is our process id
+    open(EXTRACT, "|sort >/tmp/Tmp$$")      # $$ is our process id
+	or die "Can't start sort: $!";
 
     # process argument list of files along with any includes
 
@@ -2005,7 +2104,7 @@ In the child process the filehandle isn't opened--i/o happens from/to
 the new STDOUT or STDIN.  Typically this is used like the normal
 piped open when you want to exercise more control over just how the
 pipe command gets executed, such as when you are running setuid, and
-don't want to have to scan shell commands for metacharacters.  
+don't want to have to scan shell commands for metacharacters.
 The following pairs are more or less equivalent:
 
     open(FOO, "|tr '[a-z]' '[A-Z]'");
@@ -2016,12 +2115,13 @@ The following pairs are more or less equivalent:
 
 See L<perlipc/"Safe Pipe Opens"> for more examples of this.
 
-Explicitly closing any piped filehandle causes the parent process to
-wait for the child to finish, and returns the status value in C<$?>.
-Note: on any operation which may do a fork, unflushed buffers remain
+NOTE: On any operation which may do a fork, unflushed buffers remain
 unflushed in both processes, which means you may need to set C<$|> to
 avoid duplicate output.
 
+Closing any piped filehandle causes the parent process to wait for the
+child to finish, and returns the status value in C<$?>.
+
 Using the constructor from the IO::Handle package (or one of its
 subclasses, such as IO::File or IO::Socket),
 you can generate anonymous filehandles which have the scope of whatever
@@ -2071,10 +2171,10 @@ DIRHANDLEs have their own namespace separate from FILEHANDLEs.
 
 =item ord EXPR
 
-=item ord 
+=item ord
 
 Returns the numeric ascii value of the first character of EXPR.  If
-EXPR is omitted, uses $_.  For the reverse, see L<chr>.
+EXPR is omitted, uses $_.  For the reverse, see L</chr>.
 
 =item pack TEMPLATE,LIST
 
@@ -2092,17 +2192,29 @@ follows:
 
     c	A signed char value.
     C	An unsigned char value.
+
     s	A signed short value.
     S	An unsigned short value.
+	  (This 'short' is _exactly_ 16 bits, which may differ from
+	   what a local C compiler calls 'short'.)
+
     i	A signed integer value.
     I	An unsigned integer value.
+	  (This 'integer' is _at_least_ 32 bits wide.  Its exact size
+	   depends on what a local C compiler calls 'int', and may
+	   even be larger than the 'long' described in the next item.)
+
     l	A signed long value.
     L	An unsigned long value.
+	  (This 'long' is _exactly_ 32 bits, which may differ from
+	   what a local C compiler calls 'long'.)
 
-    n	A short in "network" order.
-    N	A long in "network" order.
+    n	A short in "network" (big-endian) order.
+    N	A long in "network" (big-endian) order.
     v	A short in "VAX" (little-endian) order.
     V	A long in "VAX" (little-endian) order.
+	  (These 'shorts' and 'longs' are _exactly_ 16 bits and
+	   _exactly_ 32 bits, respectively.)
 
     f	A single-precision float in the native format.
     d	A double-precision float in the native format.
@@ -2112,10 +2224,10 @@ follows:
 
     u	A uuencoded string.
 
-    w A BER compressed integer.  Bytes give an unsigned integer base
-      128, most significant digit first, with as few digits as
-      possible, and with the bit 8 of each byte except the last set
-      to "1."
+    w	A BER compressed integer.  Its bytes represent an unsigned
+	integer in base 128, most significant digit first, with as few
+	digits as possible.  Bit eight (the high bit) is set on each
+	byte except the last.
 
     x	A null byte.
     X	Back up a byte.
@@ -2129,8 +2241,13 @@ types gobble just one value, but pack it as a string of length count,
 padding with nulls or spaces as necessary.  (When unpacking, "A" strips
 trailing spaces and nulls, but "a" does not.)  Likewise, the "b" and "B"
 fields pack a string that many bits long.  The "h" and "H" fields pack a
-string that many nybbles long.  The "P" packs a pointer to a structure of
-the size indicated by the length.  Real numbers (floats and doubles) are
+string that many nybbles long.  The "p" type packs a pointer to a null-
+terminated string.  You are responsible for ensuring the string is not a
+temporary value (which can potentially get deallocated before you get
+around to using the packed result).  The "P" packs a pointer to a structure
+of the size indicated by the length. A NULL pointer is created if the 
+corresponding value for "p" or "P" is C<undef>.
+Real numbers (floats and doubles) are
 in the native machine format only; due to the multiplicity of floating
 formats around, and the lack of a standard "network" representation, no
 facility for interchange has been made.  This means that packed floating
@@ -2205,7 +2322,7 @@ for examples of such things.
 
 =item pop ARRAY
 
-=item pop 
+=item pop
 
 Pops and returns the last value of the array, shortening the array by
 1.  Has a similar effect to
@@ -2219,7 +2336,7 @@ like shift().
 
 =item pos SCALAR
 
-=item pos 
+=item pos
 
 Returns the offset of where the last C<m//g> search left off for the variable
 is in question ($_ is used when the variable is not specified).  May be
@@ -2260,7 +2377,8 @@ you will have to use a block returning its value instead:
 
 =item printf FORMAT, LIST
 
-Equivalent to C<print FILEHANDLE sprintf(FORMAT, LIST)>.  The first argument
+Equivalent to C<print FILEHANDLE sprintf(FORMAT, LIST)>, except that $\
+(the output record separator) is not appended.  The first argument
 of the list will be interpreted as the printf format.  If C<use locale> is
 in effect, the character used for the decimal point in formatted real numbers
 is affected by the LC_NUMERIC locale.  See L<perllocale>.
@@ -2275,6 +2393,13 @@ Returns the prototype of a function as a string (or C<undef> if the
 function has no prototype).  FUNCTION is a reference to, or the name of,
 the function whose prototype you want to retrieve.
 
+If FUNCTION is a string starting with C<CORE::>, the rest is taken as
+a name for Perl builtin.  If builtin is not I<overridable> (such as
+C<qw>) or its arguments cannot be expressed by a prototype (such as
+C<system>) - in other words, the builtin does not behave like a Perl
+function - returns C<undef>.  Otherwise, the string describing the
+equivalent prototype is returned.
+
 =item push ARRAY,LIST
 
 Treats ARRAY as a stack, and pushes the values of LIST
@@ -2299,9 +2424,9 @@ Generalized quotes.  See L<perlop>.
 
 =item quotemeta EXPR
 
-=item quotemeta 
+=item quotemeta
 
-Returns the value of EXPR with with all non-alphanumeric
+Returns the value of EXPR with all non-alphanumeric
 characters backslashed.  (That is, all characters not matching
 C</[A-Za-z_0-9]/> will be preceded by a backslash in the
 returned string, regardless of any locale settings.)
@@ -2314,10 +2439,10 @@ If EXPR is omitted, uses $_.
 
 =item rand
 
-Returns a random fractional number between 0 and the value of EXPR.
-(EXPR should be positive.)  If EXPR is omitted, returns a value between 
-0 and 1.  Automatically calls srand() unless srand() has already been
-called.  See also srand().
+Returns a random fractional number greater than or equal to 0 and less
+than the value of EXPR.  (EXPR should be positive.)  If EXPR is
+omitted, the value 1 is used.  Automatically calls srand() unless
+srand() has already been called.  See also srand().
 
 (Note: If your rand function consistently returns numbers that are too
 large or too small, then your version of Perl was probably compiled
@@ -2350,23 +2475,44 @@ chdir() there, it would have been testing the wrong file.
     @dots = grep { /^\./ && -f "$some_dir/$_" } readdir(DIR);
     closedir DIR;
 
+=item readline EXPR
+
+Reads from the file handle EXPR.  In scalar context, a single line
+is read and returned.  In list context, reads until end-of-file is
+reached and returns a list of lines (however you've defined lines
+with $/ or $INPUT_RECORD_SEPARATOR).
+This is the internal function implementing the C<E<lt>EXPRE<gt>>
+operator, but you can use it directly.  The C<E<lt>EXPRE<gt>>
+operator is discussed in more detail in L<perlop/"I/O Operators">.
+
 =item readlink EXPR
 
-=item readlink 
+=item readlink
 
 Returns the value of a symbolic link, if symbolic links are
 implemented.  If not, gives a fatal error.  If there is some system
 error, returns the undefined value and sets C<$!> (errno).  If EXPR is
 omitted, uses $_.
 
+=item readpipe EXPR
+
+EXPR is interpolated and then executed as a system command.
+The collected standard output of the command is returned.
+In scalar context, it comes back as a single (potentially
+multi-line) string.  In list context, returns a list of lines
+(however you've defined lines with $/ or $INPUT_RECORD_SEPARATOR).
+This is the internal function implementing the C<qx/EXPR/>
+operator, but you can use it directly.  The C<qx/EXPR/>
+operator is discussed in more detail in L<perlop/"I/O Operators">.
+
 =item recv SOCKET,SCALAR,LEN,FLAGS
 
 Receives a message on a socket.  Attempts to receive LENGTH bytes of
 data into variable SCALAR from the specified SOCKET filehandle.
-Actually does a C recvfrom(), so that it can returns the address of the
+Actually does a C recvfrom(), so that it can return the address of the
 sender.  Returns the undefined value if there's an error.  SCALAR will
 be grown or shrunk to the length actually read.  Takes the same flags
-as the system call of the same name.  
+as the system call of the same name.
 See L<perlipc/"UDP: Message Passing"> for examples.
 
 =item redo LABEL
@@ -2398,7 +2544,7 @@ themselves about what was just input:
 
 =item ref EXPR
 
-=item ref 
+=item ref
 
 Returns a TRUE value if EXPR is a reference, FALSE otherwise.  If EXPR
 is not specified, $_ will be used.  The value returned depends on the
@@ -2412,15 +2558,15 @@ Builtin types include:
     CODE
     GLOB
 
-If the referenced object has been blessed into a package, then that package 
+If the referenced object has been blessed into a package, then that package
 name is returned instead.  You can think of ref() as a typeof() operator.
 
     if (ref($r) eq "HASH") {
 	print "r is a reference to a hash.\n";
-    } 
+    }
     if (!ref ($r) {
 	print "r is not a reference at all.\n";
-    } 
+    }
 
 See also L<perlref>.
 
@@ -2469,12 +2615,12 @@ end such a file with "1;" unless you're sure it'll return TRUE
 otherwise.  But it's better just to put the "C<1;>", in case you add more
 statements.
 
-If EXPR is a bare word, the require assumes a "F<.pm>" extension and
+If EXPR is a bareword, the require assumes a "F<.pm>" extension and
 replaces "F<::>" with "F</>" in the filename for you,
-to make it easy to load standard modules.  This form of loading of 
+to make it easy to load standard modules.  This form of loading of
 modules does not risk altering your namespace.
 
-For a yet-more-powerful import facility, see L</use> and 
+For a yet-more-powerful import facility, see L</use> and
 L<perlmod>.
 
 =item reset EXPR
@@ -2499,11 +2645,19 @@ ARGV and ENV arrays.  Resets only package variables--lexical variables
 are unaffected, but they clean themselves up on scope exit anyway,
 so you'll probably want to use them instead.  See L</my>.
 
-=item return LIST
+=item return EXPR
+
+=item return
 
-Returns from a subroutine or eval with the value specified.  (Note that
-in the absence of a return a subroutine or eval() will automatically
-return the value of the last expression evaluated.)
+Returns from a subroutine, eval(), or do FILE with the value of the
+given EXPR.  Evaluation of EXPR may be in a list, scalar, or void
+context, depending on how the return value will be used, and the context
+may vary from one execution to the next (see wantarray()).  If no EXPR
+is given, returns an empty list in a list context, an undefined value in
+a scalar context, or nothing in a void context.
+
+(Note that in the absence of a return, a subroutine, eval, or do FILE
+will automatically return the value of the last expression evaluated.)
 
 =item reverse LIST
 
@@ -2540,7 +2694,7 @@ last occurrence at or before that position.
 
 =item rmdir FILENAME
 
-=item rmdir 
+=item rmdir
 
 Deletes the directory specified by FILENAME if it is empty.  If it
 succeeds it returns 1, otherwise it returns 0 and sets C<$!> (errno).  If
@@ -2553,11 +2707,11 @@ The substitution operator.  See L<perlop>.
 =item scalar EXPR
 
 Forces EXPR to be interpreted in a scalar context and returns the value
-of EXPR.  
+of EXPR.
 
     @counts = ( scalar @a, scalar @b, scalar @c );
 
-There is no equivalent operator to force an expression to 
+There is no equivalent operator to force an expression to
 be interpolated in a list context because it's in practice never
 needed.  If you really wanted to do so, however, you could use
 the construction C<@{[ (some expression) ]}>, but usually a simple
@@ -2565,26 +2719,30 @@ C<(some expression)> suffices.
 
 =item seek FILEHANDLE,POSITION,WHENCE
 
-Randomly positions the file pointer for FILEHANDLE, just like the fseek()
-call of stdio.  FILEHANDLE may be an expression whose value gives the name
-of the filehandle.  The values for WHENCE are 0 to set the file pointer to
-POSITION, 1 to set the it to current plus POSITION, and 2 to set it to EOF
-plus offset.  You may use the values SEEK_SET, SEEK_CUR, and SEEK_END for
-this from POSIX module.  Returns 1 upon success, 0 otherwise.
+Sets FILEHANDLE's position, just like the fseek() call of stdio.
+FILEHANDLE may be an expression whose value gives the name of the
+filehandle.  The values for WHENCE are 0 to set the new position to
+POSITION, 1 to set it to the current position plus POSITION, and 2 to
+set it to EOF plus POSITION (typically negative).  For WHENCE you may
+use the constants SEEK_SET, SEEK_CUR, and SEEK_END from either the
+IO::Seekable or the POSIX module.  Returns 1 upon success, 0 otherwise.
+
+If you want to position file for sysread() or syswrite(), don't use
+seek() -- buffering makes its effect on the file's system position
+unpredictable and non-portable.  Use sysseek() instead.
 
 On some systems you have to do a seek whenever you switch between reading
 and writing.  Amongst other things, this may have the effect of calling
-stdio's clearerr(3).  A "whence" of 1 (SEEK_CUR) is useful for not moving
-the file pointer:
+stdio's clearerr(3).  A WHENCE of 1 (SEEK_CUR) is useful for not moving
+the file position:
 
     seek(TEST,0,1);
 
 This is also useful for applications emulating C<tail -f>.  Once you hit
 EOF on your read, and then sleep for a while, you might have to stick in a
-seek() to reset things.  First the simple trick listed above to clear the
-filepointer.  The seek() doesn't change the current position, but it
-I<does> clear the end-of-file condition on the handle, so that the next
-C<E<lt>FILEE<gt>> makes Perl try again to read something.  We hope.
+seek() to reset things.  The seek() doesn't change the current position,
+but it I<does> clear the end-of-file condition on the handle, so that the
+next C<E<lt>FILEE<gt>> makes Perl try again to read something.  We hope.
 
 If that doesn't work (some stdios are particularly cantankerous), then
 you may need something more like this:
@@ -2660,7 +2818,7 @@ The usual idiom is:
     ($nfound,$timeleft) =
       select($rout=$rin, $wout=$win, $eout=$ein, $timeout);
 
-or to block until something becomes ready just do this 
+or to block until something becomes ready just do this
 
     $nfound = select($rout=$rin, $wout=$win, $eout=$ein, undef);
 
@@ -2745,10 +2903,12 @@ argument.
 Shifts the first value of the array off and returns it, shortening the
 array by 1 and moving everything down.  If there are no elements in the
 array, returns the undefined value.  If ARRAY is omitted, shifts the
-@ARGV array in the main program, and the @_ array in subroutines.
-(This is determined lexically.)  See also unshift(), push(), and pop().
-Shift() and unshift() do the same thing to the left end of an array
-that pop() and push() do to the right end.
+@_ array within the lexical scope of subroutines and formats, and the
+@ARGV array at file scopes or within the lexical scopes established by
+the C<eval ''>, C<BEGIN {}>, C<END {}>, and C<INIT {}> constructs.
+See also unshift(), push(), and pop().  Shift() and unshift() do the
+same thing to the left end of an array that pop() and push() do to the
+right end.
 
 =item shmctl ID,CMD,ARG
 
@@ -2780,12 +2940,12 @@ has the same interpretation as in the system call of the same name.
 
 =item sin EXPR
 
-=item sin 
+=item sin
 
 Returns the sine of EXPR (expressed in radians).  If EXPR is omitted,
 returns sine of $_.
 
-For the inverse sine operation, you may use the POSIX::sin()
+For the inverse sine operation, you may use the POSIX::asin()
 function, or use this relation:
 
     sub asin { atan2($_[0], sqrt(1 - $_[0] * $_[0])) }
@@ -2804,8 +2964,8 @@ you requested, depending on how it counts seconds.  Most modern systems
 always sleep the full amount.
 
 For delays of finer granularity than one second, you may use Perl's
-syscall() interface to access setitimer(2) if your system supports it, 
-or else see L</select()> below.  
+syscall() interface to access setitimer(2) if your system supports it,
+or else see L</select()> below.
 
 See also the POSIX module's sigpause() function.
 
@@ -2861,7 +3021,7 @@ Examples:
     @articles = sort {$a cmp $b} @files;
 
     # now case-insensitively
-    @articles = sort { uc($a) cmp uc($b)} @files;
+    @articles = sort {uc($a) cmp uc($b)} @files;
 
     # same thing in reversed order
     @articles = sort {$b cmp $a} @files;
@@ -2892,8 +3052,8 @@ Examples:
     print sort @george, 'to', @harry;
 	    # prints AbelAxedCainPunishedcatchaseddoggonetoxyz
 
-    # inefficiently sort by descending numeric compare using 
-    # the first integer after the first = sign, or the 
+    # inefficiently sort by descending numeric compare using
+    # the first integer after the first = sign, or the
     # whole record case-insensitively otherwise
 
     @new = sort {
@@ -2906,10 +3066,10 @@ Examples:
     # we'll build auxiliary indices instead
     # for speed
     @nums = @caps = ();
-    for (@old) { 
+    for (@old) {
 	push @nums, /=(\d+)/;
 	push @caps, uc($_);
-    } 
+    }
 
     @new = @old[ sort {
 			$nums[$b] <=> $nums[$a]
@@ -2953,10 +3113,12 @@ sanity checks in the interest of speed.
 =item splice ARRAY,OFFSET
 
 Removes the elements designated by OFFSET and LENGTH from an array, and
-replaces them with the elements of LIST, if any.  Returns the elements
-removed from the array.  The array grows or shrinks as necessary.  If
-LENGTH is omitted, removes everything from OFFSET onward.  The
-following equivalences hold (assuming C<$[ == 0>):
+replaces them with the elements of LIST, if any.  In a list context,
+returns the elements removed from the array.  In a scalar context,
+returns the last element removed, or C<undef> if no elements are
+removed.  The array grows or shrinks as necessary.  If LENGTH is
+omitted, removes everything from OFFSET onward.  The following
+equivalences hold (assuming C<$[ == 0>):
 
     push(@a,$x,$y)	splice(@a,$#a+1,0,$x,$y)
     pop(@a)		splice(@a,-1)
@@ -2995,12 +3157,13 @@ value.)  The use of implicit split to @_ is deprecated, however.
 If EXPR is omitted, splits the $_ string.  If PATTERN is also omitted,
 splits on whitespace (after skipping any leading whitespace).  Anything
 matching PATTERN is taken to be a delimiter separating the fields.  (Note
-that the delimiter may be longer than one character.)  If LIMIT is
-specified and is not negative, splits into no more than that many fields
-(though it may split into fewer).  If LIMIT is unspecified, trailing null
-fields are stripped (which potential users of pop() would do well to
-remember).  If LIMIT is negative, it is treated as if an arbitrarily large
-LIMIT had been specified.
+that the delimiter may be longer than one character.)
+
+If LIMIT is specified and is not negative, splits into no more than
+that many fields (though it may split into fewer).  If LIMIT is
+unspecified, trailing null fields are stripped (which potential users
+of pop() would do well to remember).  If LIMIT is negative, it is
+treated as if an arbitrarily large LIMIT had been specified.
 
 A pattern matching the null string (not to be confused with
 a null pattern C<//>, which is just one member of the set of patterns
@@ -3030,11 +3193,11 @@ produces the list value
 
     (1, '-', 10, ',', 20)
 
-If you had the entire header of a normal Unix email message in $header, 
+If you had the entire header of a normal Unix email message in $header,
 you could split it up into fields and their values this way:
 
     $header =~ s/\n\s+/ /g;  # fix continuation lines
-    %hdrs   =  (UNIX_FROM => split /^(.*?):\s*/m, $header);
+    %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);
 
 The pattern C</PATTERN/> may be replaced with an expression to specify
 patterns that vary at runtime.  (To do runtime compilation only once,
@@ -3052,29 +3215,88 @@ Example:
 
     open(passwd, '/etc/passwd');
     while (<passwd>) {
-	($login, $passwd, $uid, $gid, $gcos, 
+	($login, $passwd, $uid, $gid, $gcos,
 	    $home, $shell) = split(/:/);
 	...
     }
 
-(Note that $shell above will still have a newline on it.  See L</chop>, 
+(Note that $shell above will still have a newline on it.  See L</chop>,
 L</chomp>, and L</join>.)
 
 =item sprintf FORMAT, LIST
 
-Returns a string formatted by the usual printf conventions of the C
-language.  See L<sprintf(3)> or L<printf(3)> on your system for details.
-(The * character for an indirectly specified length is not
-supported, but you can get the same effect by interpolating a variable
-into the pattern.)  If C<use locale> is
-in effect, the character used for the decimal point in formatted real numbers
-is affected by the LC_NUMERIC locale.  See L<perllocale>.
-Some C libraries' implementations of sprintf() can
-dump core when fed ludicrous arguments.
+Returns a string formatted by the usual printf conventions of the
+C library function sprintf().  See L<sprintf(3)> or L<printf(3)>
+on your system for an explanation of the general principles.
+
+Perl does all of its own sprintf() formatting -- it emulates the C
+function sprintf(), but it doesn't use it (except for floating-point
+numbers, and even then only the standard modifiers are allowed).  As a
+result, any non-standard extensions in your local sprintf() are not
+available from Perl.
+
+Perl's sprintf() permits the following universally-known conversions:
+
+   %%	a percent sign
+   %c	a character with the given number
+   %s	a string
+   %d	a signed integer, in decimal
+   %u	an unsigned integer, in decimal
+   %o	an unsigned integer, in octal
+   %x	an unsigned integer, in hexadecimal
+   %e	a floating-point number, in scientific notation
+   %f	a floating-point number, in fixed decimal notation
+   %g	a floating-point number, in %e or %f notation
+
+In addition, Perl permits the following widely-supported conversions:
+
+   %X	like %x, but using upper-case letters
+   %E	like %e, but using an upper-case "E"
+   %G	like %g, but with an upper-case "E" (if applicable)
+   %p	a pointer (outputs the Perl value's address in hexadecimal)
+   %n	special: *stores* the number of characters output so far
+        into the next variable in the parameter list 
+
+Finally, for backward (and we do mean "backward") compatibility, Perl
+permits these unnecessary but widely-supported conversions:
+
+   %i	a synonym for %d
+   %D	a synonym for %ld
+   %U	a synonym for %lu
+   %O	a synonym for %lo
+   %F	a synonym for %f
+
+Perl permits the following universally-known flags between the C<%>
+and the conversion letter:
+
+   space   prefix positive number with a space
+   +       prefix positive number with a plus sign
+   -       left-justify within the field
+   0       use zeros, not spaces, to right-justify
+   #       prefix non-zero octal with "0", non-zero hex with "0x"
+   number  minimum field width
+   .number "precision": digits after decimal point for floating-point,
+           max length for string, minimum length for integer
+   l       interpret integer as C type "long" or "unsigned long"
+   h       interpret integer as C type "short" or "unsigned short"
+
+There is also one Perl-specific flag:
+
+   V       interpret integer as Perl's standard integer type
+
+Where a number would appear in the flags, an asterisk ("*") may be
+used instead, in which case Perl uses the next item in the parameter
+list as the given number (that is, as the field width or precision).
+If a field width obtained through "*" is negative, it has the same
+effect as the '-' flag: left-justification.
+
+If C<use locale> is in effect, the character used for the decimal
+point in formatted real numbers is affected by the LC_NUMERIC locale.
+See L<perllocale>.
 
 =item sqrt EXPR
 
-=item sqrt 
+=item sqrt
 
 Return the square root of EXPR.  If EXPR is omitted, returns square
 root of $_.
@@ -3112,11 +3334,11 @@ function is to "seed" the rand() function so that rand() can produce
 a different sequence each time you run your program.  Just do it once at the
 top of your program, or you I<won't> get random numbers out of rand()!
 
-Frequently called programs (like CGI scripts) that simply use 
+Frequently called programs (like CGI scripts) that simply use
 
     time ^ $$
 
-for a seed can fall prey to the mathematical property that 
+for a seed can fall prey to the mathematical property that
 
     a^b == (a+1)^(b+1)
 
@@ -3126,7 +3348,7 @@ one-third of the time.  So don't do that.
 
 =item stat EXPR
 
-=item stat 
+=item stat
 
 Returns a 13-element array giving the status info for a file, either the
 file opened via FILEHANDLE, or named by EXPR.  If EXPR is omitted, it
@@ -3138,22 +3360,22 @@ follows:
        $atime,$mtime,$ctime,$blksize,$blocks)
            = stat($filename);
 
-Not all fields are supported on all filesystem types.  Here are the 
+Not all fields are supported on all filesystem types.  Here are the
 meaning of the fields:
 
-  dev	    device number of filesystem 
-  ino	    inode number 
-  mode	    file mode  (type and permissions)
-  nlink	    number of (hard) links to the file 
-  uid	    numeric user ID of file's owner 
-  gid	    numeric group ID of file's owner 
-  rdev	    the device identifier (special files only)
-  size	    total size of file, in bytes 
-  atime	    last access time since the epoch
-  mtime	    last modify time since the epoch
-  ctime	    inode change time (NOT creation time!) since the epoch
-  blksize   preferred block size for file system I/O
-  blocks    actual number of blocks allocated
+  0 dev      device number of filesystem
+  1 ino      inode number
+  2 mode     file mode  (type and permissions)
+  3 nlink    number of (hard) links to the file
+  4 uid      numeric user ID of file's owner
+  5 gid      numeric group ID of file's owner
+  6 rdev     the device identifier (special files only)
+  7 size     total size of file, in bytes
+  8 atime    last access time since the epoch
+  9 mtime    last modify time since the epoch
+ 10 ctime    inode change time (NOT creation time!) since the epoch
+ 11 blksize  preferred block size for file system I/O
+ 12 blocks   actual number of blocks allocated
 
 (The epoch was at 00:00 January 1, 1970 GMT.)
 
@@ -3175,11 +3397,11 @@ Takes extra time to study SCALAR (C<$_> if unspecified) in anticipation of
 doing many pattern matches on the string before it is next modified.
 This may or may not save time, depending on the nature and number of
 patterns you are searching on, and on the distribution of character
-frequencies in the string to be searched--you probably want to compare
+frequencies in the string to be searched -- you probably want to compare
 run times with and without it to see which runs faster.  Those loops
 which scan for many short constant strings (including the constant
 parts of more complex patterns) will benefit most.  You may have only
-one study active at a time--if you study a different scalar the first
+one study active at a time -- if you study a different scalar the first
 is "unstudied".  (The way study works is this: a linked list of every
 character in the string to be searched is made, so we know, for
 example, where all the 'k' characters are.  From each search string,
@@ -3244,11 +3466,15 @@ L<perlref> for details.
 
 Extracts a substring out of EXPR and returns it.  First character is at
 offset 0, or whatever you've set C<$[> to (but don't do that).
-If OFFSET is negative, starts
+If OFFSET is negative (or more precisely, less than C<$[>), starts
 that far from the end of the string.  If LEN is omitted, returns
 everything to the end of the string.  If LEN is negative, leaves that
 many characters off the end of the string.
 
+If you specify a substring which is partly outside the string, the part
+within the string is returned.    If the substring is totally outside
+the string a warning is produced.
+
 You can use the substr() function
 as an lvalue, in which case EXPR must be an lvalue.  If you assign
 something shorter than LEN, the string will shrink, and if you assign
@@ -3263,7 +3489,7 @@ Returns 1 for success, 0 otherwise.  On systems that don't support
 symbolic links, produces a fatal error at run time.  To check for that,
 use eval:
 
-    $symlink_exists = (eval 'symlink("","");', $@ eq '');
+    $symlink_exists = (eval {symlink("","")};, $@ eq '');
 
 =item syscall LIST
 
@@ -3273,17 +3499,32 @@ unimplemented, produces a fatal error.  The arguments are interpreted
 as follows: if a given argument is numeric, the argument is passed as
 an int.  If not, the pointer to the string value is passed.  You are
 responsible to make sure a string is pre-extended long enough to
-receive any result that might be written into a string.  If your
+receive any result that might be written into a string.  You can't use a
+string literal (or other read-only string) as an argument to syscall()
+because Perl has to assume that any string pointer might be written
+through.  If your
 integer arguments are not literals and have never been interpreted in a
 numeric context, you may need to add 0 to them to force them to look
 like numbers.
 
     require 'syscall.ph';		# may need to run h2ph
-    syscall(&SYS_write, fileno(STDOUT), "hi there\n", 9);
+    $s = "hi there\n";
+    syscall(&SYS_write, fileno(STDOUT), $s, length $s);
 
 Note that Perl supports passing of up to only 14 arguments to your system call,
 which in practice should usually suffice.
 
+Syscall returns whatever value returned by the system call it calls.
+If the system call fails, syscall returns -1 and sets C<$!> (errno).
+Note that some system calls can legitimately return -1.  The proper
+way to handle such calls is to assign C<$!=0;> before the call and
+check the value of <$!> if syscall returns -1.
+
+There's a problem with C<syscall(&SYS_pipe)>: it returns the file
+number of the read end of the pipe it creates.  There is no way
+to retrieve the file number of the other end.  You can avoid this 
+problem by using C<pipe> instead.
+
 =item sysopen FILEHANDLE,FILENAME,MODE
 
 =item sysopen FILEHANDLE,FILENAME,MODE,PERMS
@@ -3314,10 +3555,11 @@ into that kind of thing.
 
 Attempts to read LENGTH bytes of data into variable SCALAR from the
 specified FILEHANDLE, using the system call read(2).  It bypasses
-stdio, so mixing this with other kinds of reads may cause confusion.
-Returns the number of bytes actually read, or undef if there was an
-error.  SCALAR will be grown or shrunk so that the last byte actually
-read is the last byte of the scalar after the read.
+stdio, so mixing this with other kinds of reads, print(), write(),
+seek(), or tell() can cause confusion because stdio usually buffers
+data.  Returns the number of bytes actually read, or undef if there
+was an error.  SCALAR will be grown or shrunk so that the last byte
+actually read is the last byte of the scalar after the read.
 
 An OFFSET may be specified to place the read data at some place in the
 string other than the beginning.  A negative OFFSET specifies
@@ -3326,70 +3568,99 @@ string.  A positive OFFSET greater than the length of SCALAR results
 in the string being padded to the required size with "\0" bytes before
 the result of the read is appended.
 
+=item sysseek FILEHANDLE,POSITION,WHENCE
+
+Sets FILEHANDLE's system position using the system call lseek(2).  It
+bypasses stdio, so mixing this with reads (other than sysread()),
+print(), write(), seek(), or tell() may cause confusion.  FILEHANDLE may
+be an expression whose value gives the name of the filehandle.  The
+values for WHENCE are 0 to set the new position to POSITION, 1 to set
+the it to the current position plus POSITION, and 2 to set it to EOF
+plus POSITION (typically negative).  For WHENCE, you may use the
+constants SEEK_SET, SEEK_CUR, and SEEK_END from either the IO::Seekable
+or the POSIX module.
+
+Returns the new position, or the undefined value on failure.  A position
+of zero is returned as the string "0 but true"; thus sysseek() returns
+TRUE on success and FALSE on failure, yet you can still easily determine
+the new position.
+
 =item system LIST
 
+=item system PROGRAM LIST
+
 Does exactly the same thing as "exec LIST" except that a fork is done
 first, and the parent process waits for the child process to complete.
 Note that argument processing varies depending on the number of
 arguments.  The return value is the exit status of the program as
 returned by the wait() call.  To get the actual exit value divide by
-256.  See also L</exec>.  This is I<NOT> what you want to use to capture 
-the output from a command, for that you should use merely back-ticks or
+256.  See also L</exec>.  This is I<NOT> what you want to use to capture
+the output from a command, for that you should use merely backticks or
 qx//, as described in L<perlop/"`STRING`">.
 
-Because system() and back-ticks block SIGINT and SIGQUIT, killing the
+Like exec(), system() allows you to lie to a program about its name if
+you use the "system PROGRAM LIST" syntax.  Again, see L</exec>.
+
+Because system() and backticks block SIGINT and SIGQUIT, killing the
 program they're running doesn't actually interrupt your program.
 
     @args = ("command", "arg1", "arg2");
-    system(@args) == 0 
-	 or die "system @args failed: $?" 
+    system(@args) == 0
+	 or die "system @args failed: $?"
 
 Here's a more elaborate example of analysing the return value from
-system() on a UNIX system to check for all possibilities, including for
-signals and coredumps.
+system() on a Unix system to check for all possibilities, including for
+signals and core dumps.
 
     $rc = 0xffff & system @args;
     printf "system(%s) returned %#04x: ", "@args", $rc;
     if ($rc == 0) {
 	print "ran with normal exit\n";
-    } 
+    }
     elsif ($rc == 0xff00) {
 	print "command failed: $!\n";
-    } 
+    }
     elsif ($rc > 0x80) {
 	$rc >>= 8;
 	print "ran with non-zero exit status $rc\n";
-    } 
+    }
     else {
 	print "ran with ";
 	if ($rc &   0x80) {
 	    $rc &= ~0x80;
-	    print "coredump from ";
-	} 
+	    print "core dump from ";
+	}
 	print "signal $rc\n"
-    } 
+    }
     $ok = ($rc != 0);
 
+When the arguments get executed via the system shell, results will
+be subject to its quirks and capabilities.  See L<perlop/"`STRING`">
+for details.
+
 =item syswrite FILEHANDLE,SCALAR,LENGTH,OFFSET
 
 =item syswrite FILEHANDLE,SCALAR,LENGTH
 
 Attempts to write LENGTH bytes of data from variable SCALAR to the
 specified FILEHANDLE, using the system call write(2).  It bypasses
-stdio, so mixing this with prints may cause confusion.  Returns the
-number of bytes actually written, or undef if there was an error.
-If the length is greater than the available data, only as much data as
-is available will be written.
+stdio, so mixing this with reads (other than sysread()), print(),
+write(), seek(), or tell() may cause confusion because stdio usually
+buffers data.  Returns the number of bytes actually written, or undef
+if there was an error.  If the LENGTH is greater than the available
+data in the SCALAR after the OFFSET, only as much data as is available
+will be written.
 
 An OFFSET may be specified to write the data from some part of the
 string other than the beginning.  A negative OFFSET specifies writing
-from that many bytes counting backwards from the end of the string.
+that many bytes counting backwards from the end of the string.  In the
+case the SCALAR is empty you can use OFFSET but only zero offset.
 
 =item tell FILEHANDLE
 
 =item tell
 
-Returns the current file position for FILEHANDLE.  FILEHANDLE may be an
+Returns the current position for FILEHANDLE.  FILEHANDLE may be an
 expression whose value gives the name of the actual filehandle.  If
 FILEHANDLE is omitted, assumes the file last read.
 
@@ -3447,13 +3718,15 @@ A class implementing a scalar should have the following methods:
 
     TIESCALAR classname, LIST
     DESTROY this
-    FETCH this, 
+    FETCH this,
     STORE this, value
 
 Unlike dbmopen(), the tie() function will not use or require a module
 for you--you need to do that explicitly yourself.  See L<DB_File>
 or the F<Config> module for interesting tie() implementations.
 
+For further details see L<perltie>, L<tied VARIABLE>.
+
 =item tied VARIABLE
 
 Returns a reference to the object underlying VARIABLE (the same value
@@ -3477,7 +3750,7 @@ seconds, for this process and the children of this process.
 
 =item tr///
 
-The translation operator.  See L<perlop>.
+The transliteration operator.  Same as y///. See L<perlop>.
 
 =item truncate FILEHANDLE,LENGTH
 
@@ -3485,11 +3758,12 @@ The translation operator.  See L<perlop>.
 
 Truncates the file opened on FILEHANDLE, or named by EXPR, to the
 specified length.  Produces a fatal error if truncate isn't implemented
-on your system.
+on your system.  Returns TRUE if successful, the undefined value
+otherwise.
 
 =item uc EXPR
 
-=item uc 
+=item uc
 
 Returns an uppercased version of EXPR.  This is the internal function
 implementing the \U escape in double-quoted strings.
@@ -3499,7 +3773,7 @@ If EXPR is omitted, uses $_.
 
 =item ucfirst EXPR
 
-=item ucfirst 
+=item ucfirst
 
 Returns the value of EXPR with the first character uppercased.  This is
 the internal function implementing the \u escape in double-quoted strings.
@@ -3514,33 +3788,35 @@ If EXPR is omitted, uses $_.
 Sets the umask for the process to EXPR and returns the previous value.
 If EXPR is omitted, merely returns the current umask.  Remember that a
 umask is a number, usually given in octal; it is I<not> a string of octal
-digits.  See also L<oct>, if all you have is a string.
+digits.  See also L</oct>, if all you have is a string.
 
 =item undef EXPR
 
 =item undef
 
-Undefines the value of EXPR, which must be an lvalue.  Use on only a
-scalar value, an entire array or hash, or a subroutine name (using
-"&").  (Using undef() will probably not do what you expect on most
-predefined variables or DBM list values, so don't do that.)  Always
-returns the undefined value.  You can omit the EXPR, in which case
-nothing is undefined, but you still get an undefined value that you
-could, for instance, return from a subroutine, assign to a variable or
-pass as a parameter.  Examples:
+Undefines the value of EXPR, which must be an lvalue.  Use only on a
+scalar value, an array (using "@"), a hash (using "%"), a subroutine
+(using "&"), or a typeglob (using "*").  (Saying C<undef $hash{$key}>
+will probably not do what you expect on most predefined variables or
+DBM list values, so don't do that; see L<delete>.)  Always returns the
+undefined value.  You can omit the EXPR, in which case nothing is
+undefined, but you still get an undefined value that you could, for
+instance, return from a subroutine, assign to a variable or pass as a
+parameter.  Examples:
 
     undef $foo;
     undef $bar{'blurfl'};             # Compare to: delete $bar{'blurfl'};
     undef @ary;
     undef %hash;
     undef &mysub;
-    return (wantarray ? () : undef) if $they_blew_it;
+    undef *xyz;       # destroys $xyz, @xyz, %xyz, &xyz, etc.
+    return (wantarray ? (undef, $errmsg) : undef) if $they_blew_it;
     select undef, undef, undef, 0.25;
     ($a, $b, undef, $c) = &foo;       # Ignore third value returned
 
 =item unlink LIST
 
-=item unlink 
+=item unlink
 
 Deletes a list of files.  Returns the number of files successfully
 deleted.
@@ -3617,7 +3893,7 @@ package.  It is exactly equivalent to
 
     BEGIN { require Module; import Module LIST; }
 
-except that Module I<must> be a bare word.
+except that Module I<must> be a bareword.
 
 If the first argument to C<use> is a number, it is treated as a version
 number instead of a module name.  If the version of the Perl interpreter
@@ -3682,7 +3958,8 @@ Changes the access and modification times on each file of a list of
 files.  The first two elements of the list must be the NUMERICAL access
 and modification times, in that order.  Returns the number of files
 successfully changed.  The inode modification time of each file is set
-to the current time.  Example of a "touch" command:
+to the current time.  This code has the same effect as the "touch"
+command if the files already exist:
 
     #!/usr/bin/perl
     $now = time;
@@ -3745,15 +4022,25 @@ not been harvested by the Perl script yet.)
 
 Returns TRUE if the context of the currently executing subroutine is
 looking for a list value.  Returns FALSE if the context is looking
-for a scalar.
+for a scalar.  Returns the undefined value if the context is looking
+for no value (void context).
 
-    return wantarray ? () : undef;
+    return unless defined wantarray;	# don't bother doing more
+    my @a = complex_calculation();
+    return wantarray ? @a : "@a";
 
 =item warn LIST
 
 Produces a message on STDERR just like die(), but doesn't exit or throw
 an exception.
 
+If LIST is empty and $@ already contains a value (typically from a
+previous eval) that value is used after appending "\t...caught"
+to $@. This is useful for staying almost, but not entirely similar to
+die().
+
+If $@ is empty then the string "Warning: Something's wrong" is used.
+
 No message is printed if there is a C<$SIG{__WARN__}> handler
 installed.  It is the handler's responsibility to deal with the message
 as it sees fit (like, for instance, converting it into a die()).  Most
@@ -3792,7 +4079,7 @@ examples.
 
 Writes a formatted record (possibly multi-line) to the specified file,
 using the format associated with that file.  By default the format for
-a file is the one having the same name is the filehandle, but the
+a file is the one having the same name as the filehandle, but the
 format for the current output channel (see the select() function) may be set
 explicitly by assigning the name of the format to the C<$~> variable.
 
@@ -3816,6 +4103,6 @@ Note that write is I<NOT> the opposite of read.  Unfortunately.
 
 =item y///
 
-The translation operator.  See L<perlop>.
+The transliteration operator.  Same as tr///.  See L<perlop>.
 
 =back