-g File has setgid bit set.
-k File has sticky bit set.
- -T File is an ASCII text file.
+ -T File is an ASCII text file (heuristic guess).
-B File is a "binary" file (opposite of -T).
-M Age of file in days when script started.
=item chdir EXPR
-Changes the working directory to EXPR, if possible. If EXPR is omitted,
+Changes the working directory to EXPR, if possible. If EXPR is omitted,
changes to the directory specified by C<$ENV{HOME}>, if set; if not,
-changes to the directory specified by C<$ENV{LOGDIR}>. If neither is
-set, C<chdir> does nothing. It returns true upon success, false
-otherwise. See the example under C<die>.
+changes to the directory specified by C<$ENV{LOGDIR}>. (Under VMS, the
+variable C<$ENV{SYS$LOGIN}> is also checked, and used if it is set.) If
+neither is set, C<chdir> does nothing. It returns true upon success,
+false otherwise. See the example under C<die>.
=item chmod LIST
Returns the character represented by that NUMBER in the character set.
For example, C<chr(65)> is C<"A"> in either ASCII or Unicode, and
-chr(0x263a) is a Unicode smiley face. Note that characters from
-127 to 255 (inclusive) are not encoded in Unicode for backward
-compatibility reasons.
+chr(0x263a) is a Unicode smiley face. Note that characters from 127
+to 255 (inclusive) are by default not encoded in Unicode for backward
+compatibility reasons (but see L<encoding>).
For the reverse, use L</ord>.
-See L<utf8> for more about Unicode.
+See L<perlunicode> and L<encoding> for more about Unicode.
If NUMBER is omitted, uses C<$_>.
Returns an lowercased version of EXPR. This is the internal function
implementing the C<\L> escape in double-quoted strings. Respects
current LC_CTYPE locale if C<use locale> in force. See L<perllocale>
-and L<perlunicode>.
+and L<perlunicode> for more details about locale and Unicode support.
If EXPR is omitted, uses C<$_>.
Returns the value of EXPR with the first character lowercased. This
is the internal function implementing the C<\l> escape in
double-quoted strings. Respects current LC_CTYPE locale if C<use
-locale> in force. See L<perllocale> and L<perlunicode>.
+locale> in force. See L<perllocale> and L<perlunicode> for more
+details about locale and Unicode support.
If EXPR is omitted, uses C<$_>.
=item ord
-Returns the numeric (ASCII or Unicode) value of the first character of EXPR. If
-EXPR is omitted, uses C<$_>. For the reverse, see L</chr>.
-See L<utf8> for more about Unicode.
+Returns the numeric (the native 8-bit encoding, like ASCII or EBCDIC,
+or Unicode) value of the first character of EXPR. If EXPR is omitted,
+uses C<$_>.
+
+For the reverse, see L</chr>.
+See L<perlunicode> and L<encoding> for more about Unicode.
=item our EXPR
follows:
a A string with arbitrary binary data, will be null padded.
- A An ASCII string, will be space padded.
- Z A null terminated (asciz) string, will be null padded.
+ A A text (ASCII) string, will be space padded.
+ Z A null terminated (ASCIZ) string, will be null padded.
b A bit string (ascending bit order inside each byte, like vec()).
B A bit string (descending bit order inside each byte).
=item require
-Demands some semantics specified by EXPR, or by C<$_> if EXPR is not
-supplied.
+Demands a version of Perl specified by VERSION, or demands some semantics
+specified by EXPR or by C<$_> if EXPR is not supplied.
+
+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 $PERL_VERSION). A fatal error is produced at run time if
+VERSION is greater than the version of the current Perl interpreter.
+Compare with L</use>, which can do a similar check at compile time.
-If a VERSION is specified as a literal of the form v5.6.1,
-demands that the current version of Perl (C<$^V> or $PERL_VERSION) be
-at least as recent as that version, at run time. (For compatibility
-with older versions of Perl, a numeric argument will also be interpreted
-as VERSION.) Compare with L</use>, which can do a similar check at
-compile time.
+Specifying VERSION as a literal of the form v5.6.1 should generally be
+avoided, because it leads to misleading error messages under earlier
+versions of Perl which do not support this syntax. The equivalent numeric
+version should be used instead.
require v5.6.1; # run time version check
require 5.6.1; # ditto
- require 5.005_03; # float version allowed for compatibility
+ require 5.006_001; # ditto; preferred for backwards compatibility
Otherwise, demands that a library file be included if it hasn't already
been included. The file is included via the do-FILE mechanism, which is
# In the main program
push @INC, new Foo(...);
+Note that these hooks are also permitted to set the %INC entry
+corresponding to the files they have loaded. See L<perlvar/%INC>.
+
For a yet-more-powerful import facility, see L</use> and L<perlmod>.
=item reset EXPR
Any of the bit masks can also be undef. The timeout, if specified, is
in seconds, which may be fractional. Note: not all implementations are
-capable of returning the$timeleft. If not, they always return
+capable of returning the $timeleft. If not, they always return
$timeleft equal to the supplied $timeout.
You can effect a sleep of 250 milliseconds this way:
Returns an uppercased version of EXPR. This is the internal function
implementing the C<\U> escape in double-quoted strings. Respects
current LC_CTYPE locale if C<use locale> in force. See L<perllocale>
-and L<perlunicode>. Under Unicode it uses the standard Unicode
-uppercase mappings. (It does not attempt to do titlecase mapping on
-initial letters. See C<ucfirst> for that.)
+and L<perlunicode> for more details about locale and Unicode support.
+It does not attempt to do titlecase mapping on initial letters. See
+C<ucfirst> for that.
If EXPR is omitted, uses C<$_>.
Returns the value of EXPR with the first character in uppercase
(titlecase in Unicode). This is the internal function implementing
the C<\u> escape in double-quoted strings. Respects current LC_CTYPE
-locale if C<use locale> in force. See L<perllocale> and L<perlunicode>.
+locale if C<use locale> in force. See L<perllocale> and L<perlunicode>
+for more details about locale and Unicode support.
If EXPR is omitted, uses C<$_>.
except that Module I<must> be a bareword.
-VERSION, which can be specified as a literal of the form v5.6.1, demands
-that the current version of Perl (C<$^V> or $PERL_VERSION) be at least
-as recent as that version. (For compatibility with older versions of Perl,
-a numeric literal will also be interpreted as VERSION.) If the version
-of the running Perl interpreter is less than VERSION, then an error
-message is printed and Perl exits immediately without attempting to
-parse the rest of the file. Compare with L</require>, which can do a
-similar check at run time.
+VERSION may be either a numeric argument such as 5.006, which will be
+compared to C<$]>, 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.
+
+Specifying VERSION as a literal of the form v5.6.1 should generally be
+avoided, because it leads to misleading error messages under earlier
+versions of Perl which do not support this syntax. The equivalent numeric
+version should be used instead.
use v5.6.1; # compile time version check
use 5.6.1; # ditto
- use 5.005_03; # float version allowed for compatibility
+ use 5.006_001; # ditto; preferred for backwards compatibility
This is often useful if you need to check the current Perl version before
C<use>ing library modules that have changed in incompatible ways from
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