use English;
-at the top of your program. This will alias all the short names to the
-long names in the current package. Some even have medium names,
-generally borrowed from B<awk>.
+at the top of your program. This aliases all the short names to the long
+names in the current package. Some even have medium names, generally
+borrowed from B<awk>. In general, it's best to use the
-If you don't mind the performance hit, variables that depend on the
-currently selected filehandle may instead be set by calling an
-appropriate object method on the IO::Handle object. (Summary lines
-below for this contain the word HANDLE.) First you must say
+ use English '-no_match_vars';
+
+invocation if you don't need $PREMATCH, $MATCH, or $POSTMATCH, as it avoids
+a certain performance hit with the use of regular expressions. See
+L<English>.
+
+Variables that depend on the currently selected filehandle may be set by
+calling an appropriate object method on the IO::Handle object, although
+this is less efficient than using the regular built-in variables. (Summary
+lines below for this contain the word HANDLE.) First you must say
use IO::Handle;
HANDLE->method(EXPR)
Each method returns the old value of the IO::Handle attribute.
-The methods each take an optional EXPR, which if supplied specifies the
+The methods each take an optional EXPR, which, if supplied, specifies the
new value for the IO::Handle attribute in question. If not supplied,
most methods do nothing to the current value--except for
autoflush(), which will assume a 1 for you, just to be different.
+
Because loading in the IO::Handle class is an expensive operation, you should
learn how to use the regular built-in variables.
and dynamically scoped to the current BLOCK.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $PREMATCH
string.) This variable is read-only.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $POSTMATCH
This variable is read-only and dynamically scoped to the current BLOCK.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $LAST_PAREN_MATCH
pattern. (Mnemonic: the (possibly) Nested parenthesis that most
recently closed.)
-This is primarly used inside C<(?{...})> blocks for examining text
+This is primarily used inside C<(?{...})> blocks for examining text
recently matched. For example, to effectively capture text to a variable
(in addition to C<$1>, C<$2>, etc.), replace C<(...)> with
C<$.> is reset when the filehandle is closed, but B<not> when an open
filehandle is reopened without an intervening close(). For more
-details, see L<perlop/"I/O Operators">. Because C<< <> >> never does
+details, see L<perlop/"IE<sol>O Operators">. Because C<< <> >> never does
an explicit close, line numbers increase across ARGV files (but see
examples in L<perlfunc/eof>).
Also see L<Error Indicators>.
+=item ${^ENCODING}
+
+The encoding used to interpret native eight-bit encodings to Unicode,
+see L<encode>. An opaque C<Encode::XS> object.
+
=item $OS_ERROR
=item $ERRNO
=item $!
If used numerically, yields the current value of the C C<errno>
-variable, with all the usual caveats. (This means that you shouldn't
-depend on the value of C<$!> to be anything in particular unless
-you've gotten a specific error return indicating a system error.)
+variable, or in other words, if a system or library call fails, it
+sets this variable. This means that the value of C<$!> is meaningful
+only I<immediately> after a B<failure>:
+
+ if (open(FH, $filename)) {
+ # Here $! is meaningless.
+ ...
+ } else {
+ # ONLY here is $! meaningful.
+ ...
+ # Already here $! might be meaningless.
+ }
+ # Since here we might have either success or failure,
+ # here $! is meaningless.
+
+In the above I<meaningless> stands for anything: zero, non-zero,
+C<undef>. A successful system or library call does B<not> set
+the variable to zero.
+
If used an a string, yields the corresponding system error string.
You can assign a number to C<$!> to set I<errno> if, for instance,
you want C<"$!"> to return the string for error I<n>, or you want
See also the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
-The use of this variable is deprecated. The floating point representation
-can sometimes lead to inaccurate numeric comparisons. See C<$^V> for a
-more modern representation of the Perl version that allows accurate string
-comparisons.
+The floating point representation can sometimes lead to inaccurate
+numeric comparisons. See C<$^V> for a more modern representation of
+the Perl version that allows accurate string comparisons.
=item $COMPILING
is identical to C<$Config{'osname'}>. See also L<Config> and the
B<-V> command-line switch documented in L<perlrun>.
+=item ${^OPEN}
+
+An internal variable used by PerlIO. A string in two parts, separated
+by a C<\0> byte, the first part is the input disciplines, the second
+part is the output disciplines.
+
=item $PERLDB
=item $^P
epoch (beginning of 1970). The values returned by the B<-M>, B<-A>,
and B<-C> filetests are based on this value.
+=item ${^TAINT}
+
+Reflects if taint mode is on or off (i.e. if the program was run with
+B<-T> or not). True for on, false for off.
+
=item $PERL_VERSION
=item $^V
warn "No \"our\" declarations!\n" if $^V and $^V lt v5.6.0;
+To convert C<$^V> into its string representation use sprintf()'s
+C<"%vd"> conversion:
+
+ printf "version is v%vd\n", $^V; # Perl's version
+
See the documentation of C<use VERSION> and C<require VERSION>
for a convenient way to fail if the running Perl interpreter is too old.
initially consists of the arguments to any B<-I> command-line
switches, followed by the default Perl library, probably
F</usr/local/lib/perl>, followed by ".", to represent the current
-directory. If you need to modify this at runtime, you should use
+directory. ("." will not be appended if taint checks are enabled, either by
+C<-T> or by C<-t>.) If you need to modify this at runtime, you should use
the C<use lib> pragma to get the machine-dependent library properly
loaded also:
in the scope of C<use English>. For that reason, saying C<use
English> in libraries is strongly discouraged. See the
Devel::SawAmpersand module documentation from CPAN
-(http://www.perl.com/CPAN/modules/by-module/Devel/)
+(http://www.cpan.org/modules/by-module/Devel/)
for more information.
Having to even think about the C<$^S> variable in your exception