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
-names, precedence is the same as any other named unary operator, and
-the argument may be parenthesized like any other unary operator. The
+names, precedence is the same as any other named unary operator. The
operator may be any of:
-r File is readable by effective uid/gid.
be open any more when the program is reincarnated, with possible
resulting confusion on the part of Perl.
-This function is now largely obsolete, partly because it's very
-hard to convert a core file into an executable, and because the
-real compiler backends for generating portable bytecode and compilable
-C code have superseded it. That's why you should now invoke it as
-C<CORE::dump()>, if you don't want to be warned against a possible
+This function is now largely obsolete, mostly because it's very hard to
+convert a core file into an executable. That's why you should now invoke
+it as C<CORE::dump()>, if you don't want to be warned against a possible
typo.
-If you're looking to use L<dump> to speed up your program, consider
-generating bytecode or native C code as described in L<perlcc>. If
-you're just trying to accelerate a CGI script, consider using the
-C<mod_perl> extension to B<Apache>, or the CPAN module, CGI::Fast.
-You might also consider autoloading or selfloading, which at least
-make your program I<appear> to run faster.
-
=item each HASH
X<each> X<hash, iterator>
=item no Module
+=item no VERSION
+
See the C<use> function, of which C<no> is the opposite.
=item oct EXPR
H A hex string (high nybble first).
c A signed char (8-bit) value.
- C An unsigned C char (octet) even under Unicode. Should normally not
- be used. See U and W instead.
+ C An unsigned char (octet) value.
W An unsigned char value (can be greater than 255).
s A signed short (16-bit) value.
P A pointer to a structure (fixed-length string).
u A uuencoded string.
- U A Unicode character number. Encodes to UTF-8 internally
- (or UTF-EBCDIC in EBCDIC platforms).
+ U A Unicode character number. Encodes to a character in character mode
+ and UTF-8 (or UTF-EBCDIC in EBCDIC platforms) in byte mode.
w A BER compressed integer (not an ASN.1 BER, see perlpacktut for
details). Its bytes represent an unsigned integer in base 128,
closedir DIR;
=item readline EXPR
+
+=item readline
X<readline> X<gets> X<fgets>
-Reads from the filehandle whose typeglob is contained in EXPR. In scalar
-context, each call reads and returns the next line, until end-of-file is
-reached, whereupon the subsequent call returns undef. In list context,
-reads until end-of-file is reached and returns a list of lines. Note that
-the notion of "line" used here is however you may have defined it
-with C<$/> or C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
+Reads from the filehandle whose typeglob is contained in EXPR (or from
+*ARGV if EXPR is not provided). In scalar context, each call reads and
+returns the next line, until end-of-file is reached, whereupon the
+subsequent call returns undef. In list context, reads until end-of-file
+is reached and returns a list of lines. Note that the notion of "line"
+used here is however you may have defined it with C<$/> or
+C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
When C<$/> is set to C<undef>, when readline() is in scalar
context (i.e. file slurp mode), and when an empty file is read, it
omitted, uses C<$_>.
=item readpipe EXPR
+
+=item readpipe
X<readpipe>
EXPR is executed as a system command.
This is the internal function implementing the C<qx/EXPR/>
operator, but you can use it directly. The C<qx/EXPR/>
operator is discussed in more detail in L<perlop/"I/O Operators">.
+If EXPR is omitted, uses C<$_>.
=item recv SOCKET,SCALAR,LENGTH,FLAGS
X<recv>
print "r is not a reference at all.\n";
}
+The return value C<LVALUE> indicates a reference to an lvalue that is not
+a variable. You get this from taking the reference of function calls like
+C<pos()> or C<substr()>. C<VSTRING> is returned if the reference points
+to a L<version string|perldata\"Version Strings">.
+
+The result C<Regexp> indicates that the argument is a regular expression
+resulting from C<qr//>.
+
See also L<perlref>.
=item rename OLDNAME,NEWNAME
Otherwise, C<require> demands that a library file be included if it
hasn't already been included. The file is included via the do-FILE
-mechanism, which is essentially just a variety of C<eval>. Has
-semantics similar to the following subroutine:
+mechanism, which is essentially just a variety of C<eval> with the
+caveat that lexical variables in the invoking script will be invisible
+to the included code. Has semantics similar to the following subroutine:
sub require {
my ($filename) = @_;
=item say
Just like C<print>, but implicitly appends a newline.
-C<say LIST> is simply an abbreviation for C<{ local $/ = "\n"; print
+C<say LIST> is simply an abbreviation for C<{ local $\ = "\n"; print
LIST }>.
This keyword is only available when the "say" feature is
=item select
-Returns the currently selected filehandle. Sets the current default
-filehandle for output, if FILEHANDLE is supplied. This has two
+Returns the currently selected filehandle. If FILEHANDLE is supplied,
+sets the new current default filehandle for output. This has two
effects: first, a C<write> or a C<print> without a filehandle will
default to this FILEHANDLE. Second, references to variables related to
output will refer to this output channel. For example, if you have to
=item state TYPE EXPR : ATTRS
C<state> declares a lexically scoped variable, just like C<my> does.
-However, those variables will be initialized only once, contrary to
+However, those variables will never be reinitialized, contrary to
lexical variables that are reinitialized each time their enclosing block
is entered.
except that Module I<must> be a bareword.
-VERSION may be either a numeric argument such as 5.006, which will be
-compared to C<$]>, or a literal of the form v5.6.1, which will be compared
-to C<$^V> (aka $PERL_VERSION). A fatal error is produced if VERSION is
-greater than the version of the current Perl interpreter; Perl will not
-attempt to parse the rest of the file. Compare with L</require>, which can
-do a similar check at run time.
+In the peculiar C<use VERSION> form, VERSION may be either a numeric
+argument such as 5.006, which will be compared to C<$]>, or a literal of
+the form v5.6.1, which will be compared to C<$^V> (aka $PERL_VERSION). A
+fatal error is produced if VERSION is greater than the version of the
+current Perl interpreter; Perl will not attempt to parse the rest of the
+file. Compare with L</require>, which can do a similar check at run time.
+Symmetrically, C<no VERSION> allows you to specify that you want a version
+of perl older than the specified one.
Specifying VERSION as a literal of the form v5.6.1 should generally be
avoided, because it leads to misleading error messages under earlier
C<use>ing library modules that have changed in incompatible ways from
older versions of Perl. (We try not to do this more than we have to.)
-If the specified perl version is greater than or equal to 5.9.5, C<use
-VERSION> will also load the C<feature> pragma and enable all features
-available in the requested version. See L<feature>.
+Also, if the specified perl version is greater than or equal to 5.9.5,
+C<use VERSION> will also load the C<feature> pragma and enable all
+features available in the requested version. See L<feature>.
The C<BEGIN> forces the C<require> and C<import> to happen at compile time. The
C<require> makes sure the module is loaded into memory if it hasn't been
projects / p5sagit/p5-mst-13.2.git / blobdiff