=item Keywords related to switch
-C<break>, C<continue>
+C<break>, C<continue>, C<given>, C<when>, C<default>
(These are only available if you enable the "switch" feature.
See L<feature> and L<perlsyn/"Switch statements">.)
=item Keywords related to scoping
-C<caller>, C<import>, C<local>, C<my>, C<our>, C<package>, C<use>
+C<caller>, C<import>, C<local>, C<my>, C<our>, C<state>, C<package>,
+C<use>
+
+(C<state> is only available if the "state" feature is enabled. See
+L<feature>.)
=item Miscellaneous functions
-C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>, C<reset>,
-C<scalar>, C<undef>, C<wantarray>
+C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>,
+C<reset>, C<scalar>, C<state>, C<undef>, C<wantarray>
=item Functions for processes and process groups
X<process> X<pid> X<process id>
=item Functions new in perl5
X<perl5>
-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<our>, 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<abs>, C<bless>, C<break>, C<chomp>, C<chr>, C<continue>, C<default>,
+C<exists>, C<formline>, C<given>, C<glob>, C<import>, C<lc>, C<lcfirst>,
+C<lock>, C<map>, C<my>, C<no>, C<our>, C<prototype>, C<qr>, C<qw>, C<qx>,
+C<readline>, C<readpipe>, C<ref>, C<sub>*, C<sysopen>, C<tie>, C<tied>, C<uc>,
+C<ucfirst>, C<untie>, C<use>, C<when>
* - C<sub> was a keyword in perl4, but in perl5 it is an
operator, which can be used in expressions.
=item -X EXPR
+=item -X DIRHANDLE
+
=item -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
-tests the associated file to see if something is true about it. If the
+operator takes one argument, either a filename, a filehandle, or a dirhandle,
+and tests the associated file to see if something is true about it. If the
argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.
Unless otherwise documented, it returns C<1> for true and C<''> for false, or
the undefined value if the file doesn't exist. Despite the funny
to go back before the current one.
($package, $filename, $line, $subroutine, $hasargs,
- $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);
+ $wantarray, $evaltext, $is_require, $hints, $bitmask, $hinthash)
+ = caller($i);
Here $subroutine may be C<(eval)> if the frame is not a subroutine
call, but an C<eval>. In such a case additional elements $evaltext and
compiled with. The C<$hints> and C<$bitmask> values are subject to change
between versions of Perl, and are not meant for external use.
+C<$hinthash> is a reference to a hash containing the value of C<%^H> when the
+caller was compiled, or C<undef> if C<%^H> was empty. Do not modify the values
+of this hash, as they are the actual values stored in the optree.
+
Furthermore, when called from within the DB package, caller returns more
detailed information: it sets the list variable C<@DB::args> to be the
arguments with which the subroutine was invoked.
On systems that support fchmod, you might pass file handles among the
files. On systems that don't support fchmod, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
open(my $fh, "<", "foo");
my $perm = (stat $fh)[2] & 07777;
On systems that support fchown, you might pass file handles among the
files. On systems that don't support fchown, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
Here's an example that looks up nonnumeric uids in the passwd file:
$cnt = kill 1, $child1, $child2;
kill 9, @goners;
-If SIGNAL is zero, no signal is sent to the process. This is a
-useful way to check that a child process is alive and hasn't changed
-its UID. See L<perlport> for notes on the portability of this
-construct.
+If SIGNAL is zero, no signal is sent to the process, but the kill(2)
+system call will check whether it's possible to send a signal to it (that
+means, to be brief, that the process is owned by the same user, or we are
+the super-user). This is a useful way to check that a child process is
+alive and hasn't changed its UID. See L<perlport> for notes on the
+portability of this construct.
Unlike in the shell, if SIGNAL is negative, it kills
process groups instead of processes. (On System V, a negative I<PROCESS>
=item our EXPR
X<our> X<global>
-=item our EXPR TYPE
+=item our TYPE EXPR
=item our EXPR : ATTRS
L<perlsub/"Private Variables via my()"> for details, and L<fields>,
L<attributes>, and L<Attribute::Handlers>.
-The only currently recognized C<our()> attribute is C<unique> which
-indicates that a single copy of the global is to be used by all
-interpreters should the program happen to be running in a
-multi-interpreter environment. (The default behaviour would be for
-each interpreter to have its own copy of the global.) Examples:
-
- our @EXPORT : unique = qw(foo);
- our %EXPORT_TAGS : unique = (bar => [qw(aa bb cc)]);
- our $VERSION : unique = "1.00";
-
-Note that this attribute also has the effect of making the global
-readonly when the first new interpreter is cloned (for example,
-when the first new thread is created).
-
-Multi-interpreter environments can come to being either through the
-fork() emulation on Windows platforms, or by embedding perl in a
-multi-threaded application. The C<unique> attribute does nothing in
-all other environments.
-
-Warning: the current implementation of this attribute operates on the
-typeglob associated with the variable; this means that C<our $x : unique>
-also has the effect of C<our @x : unique; our %x : unique>. This may be
-subject to change.
-
=item pack TEMPLATE,LIST
X<pack>
I A unsigned integer value.
(This 'integer' is _at_least_ 32 bits wide. Its exact
size depends on what a local C compiler calls 'int'.)
-
+
n An unsigned short (16-bit) in "network" (big-endian) order.
N An unsigned long (32-bit) in "network" (big-endian) order.
v An unsigned short (16-bit) in "VAX" (little-endian) order.
The C</> template character allows packing and unpacking of a sequence of
items where the packed structure contains a packed item count followed by
the packed items themselves.
-You write I<length-item>C</>I<sequence-item>.
-The I<length-item> can be any C<pack> template letter, and describes
-how the length value is packed. The ones likely to be of most use are
-integer-packing ones like C<n> (for Java strings), C<w> (for ASN.1 or
-SNMP) and C<N> (for Sun XDR).
+For C<pack> you write I<length-item>C</>I<sequence-item> and the
+I<length-item> describes how the length value is packed. The ones likely
+to be of most use are integer-packing ones like C<n> (for Java strings),
+C<w> (for ASN.1 or SNMP) and C<N> (for Sun XDR).
For C<pack>, the I<sequence-item> may have a repeat count, in which case
the minimum of that and the number of available items is used as argument
for the I<length-item>. If it has no repeat count or uses a '*', the number
-of available items is used. For C<unpack> the repeat count is always obtained
-by decoding the packed item count, and the I<sequence-item> must not have a
-repeat count.
+of available items is used.
+
+For C<unpack> an internal stack of integer arguments unpacked so far is
+used. You write C</>I<sequence-item> and the repeat count is obtained by
+popping off the last element from the stack. The I<sequence-item> must not
+have a repeat count.
If the I<sequence-item> refers to a string type (C<"A">, C<"a"> or C<"Z">),
the I<length-item> is a string length, not a number of strings. If there is
an explicit repeat count for pack, the packed string will be adjusted to that
given length.
- unpack 'W/a', "\04Gurusamy"; gives ('Guru')
- unpack 'a3/A* A*', '007 Bond J '; gives (' Bond', 'J')
- pack 'n/a* w/a','hello,','world'; gives "\000\006hello,\005world"
- pack 'a/W2', ord('a') .. ord('z'); gives '2ab'
+ unpack 'W/a', "\04Gurusamy"; gives ('Guru')
+ unpack 'a3/A A*', '007 Bond J '; gives (' Bond', 'J')
+ unpack 'a3 x2 /A A*', '007: Bond, J.'; gives ('Bond, J', '.')
+ pack 'n/a* w/a','hello,','world'; gives "\000\006hello,\005world"
+ pack 'a/W2', ord('a') .. ord('z'); gives '2ab'
The I<length-item> is not returned explicitly from C<unpack>.
REF
GLOB
LVALUE
+ FORMAT
+ IO
+ VSTRING
+ Regexp
If the referenced object has been blessed into a package, then that package
name is returned instead. You can think of C<ref> as a C<typeof> operator.
eval "require $class";
-Now that you understand how C<require> looks for files in the case of
-a bareword argument, there is a little extra functionality going on
-behind the scenes. Before C<require> looks for a "F<.pm>" extension,
-it will first look for a filename with a "F<.pmc>" extension. A file
-with this extension is assumed to be Perl bytecode generated by
-L<B::Bytecode|B::Bytecode>. If this file is found, and its modification
-time is newer than a coinciding "F<.pm>" non-compiled file, it will be
-loaded in place of that non-compiled file ending in a "F<.pm>" extension.
+Now that you understand how C<require> looks for files in the case of a
+bareword argument, there is a little extra functionality going on behind
+the scenes. Before C<require> looks for a "F<.pm>" extension, it will
+first look for a similar filename with a "F<.pmc>" extension. If this file
+is found, it will be loaded in place of any file ending in a "F<.pm>"
+extension.
You can also insert hooks into the import facility, by putting directly
Perl code into the @INC array. There are three forms of hooks: subroutine
walks through @INC and encounters a subroutine, this subroutine gets
called with two parameters, the first being a reference to itself, and the
second the name of the file to be included (e.g. "F<Foo/Bar.pm>"). The
-subroutine should return C<undef> or a filehandle, from which the file to
-include will be read. If C<undef> is returned, C<require> will look at
-the remaining elements of @INC.
+subroutine should return nothing, or a list of up to 4 values in the
+following order:
+
+=over
+
+=item 1
+
+A reference to a scalar, containing any initial source code to prepend to
+the file or generator output.
+
+
+=item 2
+
+A filehandle, from which the file will be read.
+
+=item 3
+
+A reference to a subroutine. If there is no file handle, then this subroutine
+is expected to generate one line of source code per call, writing the line
+into C<$_> and returning 1, then returning 0 at "end of FILE" If there is a
+file handle then the subroutine will be called to act a simple source filter,
+with the line as read in C<$_>. Again, return 1 for each valid line, and 0
+after all lines have been returned.
+
+=item 4
+
+Optional state for the subroutine. The state is passed in as C<$_[1]>. A
+reference to the subroutine itself is passed in as C<$_[0]>.
+
+=back
+
+If an empty list, C<undef>, or nothing that matches the first 3 values above
+is returned then C<require> will look at the remaining elements of @INC.
+Note that this file handle must be a real file handle (strictly a typeglob,
+or reference to a typeglob, blessed or unblessed) - tied file handles will be
+ignored and return value processing will stop there.
If the hook is an array reference, its first element must be a subroutine
reference. This subroutine is called as above, but the first parameter is
If the hook is an object, it must provide an INC method that will be
called as above, the first parameter being the object itself. (Note that
-you must fully qualify the sub's name, as it is always forced into package
-C<main>.) Here is a typical code layout:
+you must fully qualify the sub's name, as unqualified C<INC> is always forced
+into package C<main>.) Here is a typical code layout:
# In Foo.pm
package Foo;
=item stat EXPR
+=item stat DIRHANDLE
+
=item stat
Returns a 13-element list giving the status info for a file, either
-the file opened via FILEHANDLE, or named by EXPR. If EXPR is omitted,
-it stats C<$_>. Returns a null list if the stat fails. Typically used
-as follows:
+the file opened via FILEHANDLE or DIRHANDLE, or named by EXPR. If EXPR is
+omitted, it stats C<$_>. Returns a null list if the stat fails. Typically
+used as follows:
($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
$atime,$mtime,$ctime,$blksize,$blocks)
about the C<S_*> constants. To get status info for a symbolic link
instead of the target file behind the link, use the C<lstat> function.
+=item state EXPR
+X<state>
+
+=item state TYPE EXPR
+
+=item state EXPR : ATTRS
+
+=item state TYPE EXPR : ATTRS
+
+C<state> declares a lexically scoped variable, just like C<my> does.
+However, those variables will be initialized only once, contrary to
+lexical variables that are reinitialized each time their enclosing block
+is entered.
+
+C<state> variables are only enabled when the C<feature 'state'> pragma is
+in effect. See L<feature>.
+
=item study SCALAR
X<study>
everything to the end of the string. If LENGTH is negative, leaves that
many characters off the end of the string.
+ my $s = "The black cat climbed the green tree";
+ my $color = substr $s, 4, 5; # black
+ my $middle = substr $s, 4, -11; # black cat climbed the
+ my $end = substr $s, 14; # climbed the green tree
+ my $tail = substr $s, -4; # tree
+ my $z = substr $s, -4, 2; # tr
+
You can use the substr() function as an lvalue, in which case EXPR
must itself be an lvalue. If you assign something shorter than LENGTH,
the string will shrink, and if you assign something longer than LENGTH,
parts of the EXPR and return what was there before in one operation,
just as you can with splice().
+ my $s = "The black cat climbed the green tree";
+ my $z = substr $s, 14, 7, "jumped from"; # climbed
+ # $s is now "The black cat jumped from the green tree"
+
Note that the lvalue returned by the 3-arg version of substr() acts as
a 'magic bullet'; each time it is assigned to, it remembers which part
of the original string is being modified; for example:
$_ = 'pq'; print $x,"\n"; # prints 5pq9
}
-
Prior to Perl version 5.9.1, the result of using an lvalue multiple times was
unspecified.
In scalar context, C<times> returns C<$user>.
+Note that times for children are included only after they terminate.
+
=item tr///
The transliteration operator. Same as C<y///>. See L<perlop>.
The behavior is undefined if LENGTH is greater than the length of the
file.
+The position in the file of FILEHANDLE is left unchanged. You may want to
+call L<seek> before writing to the file.
+
=item uc EXPR
X<uc> X<uppercase> X<toupper>
On systems that support futimes, you might pass file handles among the
files. On systems that don't support futimes, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
=item values HASH
X<values>
#...
do {
$kid = waitpid(-1, WNOHANG);
- } until $kid > 0;
+ } while $kid > 0;
then you can do a non-blocking wait for all pending zombie processes.
Non-blocking wait is available on machines supporting either the
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