=head2 Predefined Names
-The following names have special meaning to Perl. Most of the
+The following names have special meaning to Perl. Most
punctuation names have reasonable mnemonics, or analogues in one of
-the shells. Nevertheless, if you wish to use the long variable names,
+the shells. Nevertheless, if you wish to use long variable names,
you just need to say
use English;
at the top of your program. This will alias all the short names to the
-long names in the current package. Some of them even have medium names,
+long names in the current package. Some even have medium names,
generally borrowed from B<awk>.
To go a step further, those variables that depend on the currently
method HANDLE EXPR
-or
+or more safely,
HANDLE->method(EXPR)
=over 8
-=item $E<lt>I<digit>E<gt>
+=item $E<lt>I<digits>E<gt>
Contains the subpattern from the corresponding set of parentheses in
the last pattern matched, not counting patterns matched in nested
-blocks that have been exited already. (Mnemonic: like \digit.)
+blocks that have been exited already. (Mnemonic: like \digits.)
These variables are all read-only.
=item $MATCH
influences the interpretation of only "C<^>" and "C<$>". A literal newline can
be searched for even when C<$* == 0>.
-Use of "C<$*>" is deprecated in modern perls.
+Use of "C<$*>" is deprecated in modern Perls, supplanted by
+the C</s> and C</m> modifiers on pattern matching.
=item input_line_number HANDLE EXPR
Remember: the value of $/ is a string, not a regexp. AWK has to be
better for something :-)
+Setting $/ to a reference to an integer, scalar containing an integer, or
+scalar that's convertable to an integer will attempt to read records
+instead of lines, with the maximum record size being the referenced
+integer. So this:
+
+ $/ = \32768; # or \"32768", or \$var_containing_32768
+ open(FILE, $myfile);
+ $_ = <FILE>;
+
+will read a record of no more than 32768 bytes from FILE. If you're not
+reading from a record-oriented file (or your OS doesn't have
+record-oriented files), then you'll likely get a full chunk of data with
+every read. If a record is larger than the record size you've set, you'll
+get the record back in pieces.
+
+On VMS, record reads are done with the equivalent of C<sysread>, so it's
+best not to mix record and non-record reads on the same file. (This is
+likely not a problem, as any file you'd want to read in record mode is
+proably usable in line mode) Non-VMS systems perform normal I/O, so
+it's safe to mix record and non-record reads of a file.
+
=item autoflush HANDLE EXPR
=item $OUTPUT_AUTOFLUSH
=item $?
The status returned by the last pipe close, backtick (C<``>) command,
-or system() operator. Note that this is the status word returned by
-the wait() system call (or else is made up to look like it). Thus,
-the exit value of the subprocess is actually (C<$? E<gt>E<gt> 8>), and
-C<$? & 255> gives which signal, if any, the process died from, and
-whether there was a core dump. (Mnemonic: similar to B<sh> and
-B<ksh>.)
+or system() operator. Note that this is the status word returned by the
+wait() system call (or else is made up to look like it). Thus, the exit
+value of the subprocess is actually (C<$? E<gt>E<gt> 8>), and C<$? & 127>
+gives which signal, if any, the process died from, and C<$? & 128> reports
+whether there was a core dump. (Mnemonic: similar to B<sh> and B<ksh>.)
+
+Additionally, if the C<h_errno> variable is supported in C, its value
+is returned via $? if any of the C<gethost*()> functions fail.
Note that if you have installed a signal handler for C<SIGCHLD>, the
value of C<$?> will usually be wrong outside that handler.
system error than that provided by C<$!>. This is particularly
important when C<$!> is set to B<EVMSERR>.
-Under OS/2, C<$^E> is set based on the value returned by the OS/2
-call C<_syserrno()> only when a call into the OS/2 API generates
-an error. In this case, C<$!> is set to a special value to
-indicate that C<$^E> should be checked. Otherwise, C<$^E> is
-just the same as C<$!>.
+Under OS/2, C<$^E> is set to the error code of the last call to
+OS/2 API either via CRT, or directly from perl.
Under Win32, C<$^E> always returns the last error information
reported by the Win32 call C<GetLastError()> which describes
Current state of the interpreter. Undefined if parsing of the current
module/eval is not finished (may happen in $SIG{__DIE__} and
-$SIG{__WARN__} handlers). True if inside an eval, othewise false.
+$SIG{__WARN__} handlers). True if inside an eval, otherwise false.
=item $BASETIME
can die from a C<__DIE__> handler. Similarly for C<__WARN__>.
Note that the C<$SIG{__DIE__}> hook is called even inside eval()ed
-blocks/strings. See L<perlfunc/die>
, L<perlvar/$^S> for how to
+blocks/strings. See L<perlfunc/die>
and L<perlvar/$^S> for how to
circumvent this.
Note that C<__DIE__>/C<__WARN__> handlers are very special in one
https://perl5.git.perl.org / perl5.git / blobdiff