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@kozachkov
kozachkov committed May 15, 2021
2 parents f212efc + 01f4356 commit 8233509
Showing 1 changed file with 87 additions and 87 deletions.
174 changes: 87 additions & 87 deletions pod/perlvar.pod
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Expand Up @@ -371,7 +371,7 @@ it really means

But don't put

@foo{$x,$y,$z} # a slice--note the @
@foo{$x,$y,$z} # a slice--note the @

which means

Expand Down Expand Up @@ -593,11 +593,11 @@ X<%SIG>
The hash C<%SIG> contains signal handlers for signals. For example:

sub handler { # 1st argument is signal name
my($sig) = @_;
print "Caught a SIG$sig--shutting down\n";
close(LOG);
exit(0);
}
my($sig) = @_;
print "Caught a SIG$sig--shutting down\n";
close(LOG);
exit(0);
}

$SIG{'INT'} = \&handler;
$SIG{'QUIT'} = \&handler;
Expand All @@ -613,12 +613,12 @@ the same effect as C<'DEFAULT'>.
Here are some other examples:

$SIG{"PIPE"} = "Plumber"; # assumes main::Plumber (not
# recommended)
# recommended)
$SIG{"PIPE"} = \&Plumber; # just fine; assume current
# Plumber
# Plumber
$SIG{"PIPE"} = *Plumber; # somewhat esoteric
$SIG{"PIPE"} = Plumber(); # oops, what did Plumber()
# return??
# return??

Be sure not to use a bareword as the name of a signal handler,
lest you inadvertently call it.
Expand Down Expand Up @@ -747,13 +747,6 @@ the behavior of C<$]> is unchanged on all versions of Perl.

Mnemonic: use ^V for a version object.

=item ${^WIN32_SLOPPY_STAT}
X<${^WIN32_SLOPPY_STAT}> X<sitecustomize> X<sitecustomize.pl>

This variable no longer has any function.

This variable was added in Perl v5.10.0 and removed in Perl v5.34.0.

=item $EXECUTABLE_NAME

=item $^X
Expand Down Expand Up @@ -789,9 +782,9 @@ following statements:
use Config;
my $this_perl = $^X;
if ($^O ne 'VMS') {
$this_perl .= $Config{_exe}
unless $this_perl =~ m/$Config{_exe}$/i;
}
$this_perl .= $Config{_exe}
unless $this_perl =~ m/$Config{_exe}$/i;
}

Because many operating systems permit anyone with read access to
the Perl program file to make a copy of it, patch the copy, and
Expand All @@ -804,9 +797,9 @@ command or referenced as a file.
use Config;
my $secure_perl_path = $Config{perlpath};
if ($^O ne 'VMS') {
$secure_perl_path .= $Config{_exe}
unless $secure_perl_path =~ m/$Config{_exe}$/i;
}
$secure_perl_path .= $Config{_exe}
unless $secure_perl_path =~ m/$Config{_exe}$/i;
}

=back

Expand All @@ -817,8 +810,8 @@ effects. Perl sets these variables when it has a successful match, so
you should check the match result before using them. For instance:

if( /P(A)TT(ER)N/ ) {
print "I found $1 and $2\n";
}
print "I found $1 and $2\n";
}

These variables are read-only and dynamically-scoped, unless we note
otherwise.
Expand All @@ -836,13 +829,13 @@ by this bit of code:

{
OUTER:
show_n() if $outer =~ m/$pattern/;
show_n() if $outer =~ m/$pattern/;

INNER: {
show_n() if $inner =~ m/$pattern/;
}
INNER: {
show_n() if $inner =~ m/$pattern/;
}

show_n();
show_n();
}

The output shows that while in the C<OUTER> block, the values of C<$1>
Expand Down Expand Up @@ -875,9 +868,9 @@ this:
print $`, $&, $'; # bad: performance hit

print # good: no performance hit
substr($str, 0, $-[0]),
substr($str, $-[0], $+[0]-$-[0]),
substr($str, $+[0]);
substr($str, 0, $-[0]),
substr($str, $-[0], $+[0]-$-[0]),
substr($str, $+[0]);

In Perl 5.10.0 the C</p> match operator flag and the C<${^PREMATCH}>,
C<${^MATCH}>, and C<${^POSTMATCH}> variables were introduced, that allowed
Expand Down Expand Up @@ -1021,7 +1014,7 @@ enclosed by the current BLOCK). Example:

local $_ = 'abcdefghi';
/def/;
print "$`:$&:$'\n"; # prints abc:def:ghi
print "$`:$&:$'\n"; # prints abc:def:ghi

See L</Performance issues> above for the serious performance implications
of using this variable (even once) in your code.
Expand Down Expand Up @@ -1352,22 +1345,22 @@ example:
my $content = '';
open my $fh, "<", "foo" or die $!;
{
local $/;
$content = <$fh>;
local $/;
$content = <$fh>;
}
close $fh;

Here is an example of how your own code can go broken:

for ( 1..3 ){
$\ = "\r\n";
nasty_break();
print "$_";
$\ = "\r\n";
nasty_break();
print "$_";
}

sub nasty_break {
$\ = "\f";
# do something with $_
$\ = "\f";
# do something with $_
}

You probably expect this code to print the equivalent of
Expand Down Expand Up @@ -1757,9 +1750,9 @@ execution of this statement, perl may have set all four special error
variables:

eval q{
open my $pipe, "/cdrom/install |" or die $!;
my @res = <$pipe>;
close $pipe or die "bad pipe: $?, $!";
open my $pipe, "/cdrom/install |" or die $!;
my @res = <$pipe>;
close $pipe or die "bad pipe: $?, $!";
};

When perl executes the C<eval()> expression, it translates the
Expand Down Expand Up @@ -1844,11 +1837,11 @@ X<$^S> X<$EXCEPTIONS_BEING_CAUGHT>

Current state of the interpreter.

$^S State
--------- -------------------------------------
undef Parsing module, eval, or main program
true (1) Executing an eval
false (0) Otherwise
$^S State
--------- -------------------------------------
undef Parsing module, eval, or main program
true (1) Executing an eval
false (0) Otherwise

The first state may happen in C<$SIG{__DIE__}> and C<$SIG{__WARN__}>
handlers.
Expand Down Expand Up @@ -1901,13 +1894,13 @@ non-zero value on success. This means C<errno>, hence C<$!>, is
meaningful only I<immediately> after a B<failure>:

if (open my $fh, "<", $filename) {
# Here $! is meaningless.
...
# Here $! is meaningless.
...
}
else {
# ONLY here is $! meaningful.
...
# Already here $! might be meaningless.
# ONLY here is $! meaningful.
...
# Already here $! might be meaningless.
}
# Since here we might have either success or failure,
# $! is meaningless.
Expand Down Expand Up @@ -1967,7 +1960,7 @@ given to C<exit()>. You can modify C<$?> in an C<END> subroutine to
change the exit status of your program. For example:

END {
$? = 1 if $? == 255; # die would make it 255
$? = 1 if $? == 255; # die would make it 255
}

Under VMS, the pragma C<use vmsish 'status'> makes C<$?> reflect the
Expand Down Expand Up @@ -2028,36 +2021,6 @@ debugger operation. See L<perldebguts/Debugger Internals>.

Mnemonic: value of B<-D> switch.

=item ${^ENCODING}
X<${^ENCODING}>

This variable is no longer supported.

It used to hold the I<object reference> to the C<Encode> object that was
used to convert the source code to Unicode.

Its purpose was to allow your non-ASCII Perl
scripts not to have to be written in UTF-8; this was
useful before editors that worked on UTF-8 encoded text were common, but
that was long ago. It caused problems, such as affecting the operation
of other modules that weren't expecting it, causing general mayhem.

If you need something like this functionality, it is recommended that use
you a simple source filter, such as L<Filter::Encoding>.

If you are coming here because code of yours is being adversely affected
by someone's use of this variable, you can usually work around it by
doing this:

local ${^ENCODING};

near the beginning of the functions that are getting broken. This
undefines the variable during the scope of execution of the including
function.

This variable was added in Perl 5.8.2 and removed in 5.26.0.
Setting it to anything other than C<undef> was made fatal in Perl 5.28.0.

=item ${^GLOBAL_PHASE}
X<${^GLOBAL_PHASE}>

Expand Down Expand Up @@ -2191,8 +2154,8 @@ different pragmatic flags. Here's an example:
sub add_100 { $^H |= 0x100 }

sub foo {
BEGIN { add_100() }
bar->baz($boon);
BEGIN { add_100() }
bar->baz($boon);
}

Consider what happens during execution of the BEGIN block. At this point
Expand All @@ -2209,7 +2172,7 @@ demonstrates how C<use strict 'vars'> is implemented. Here's a conditional
version of the same lexical pragma:

BEGIN {
require strict; strict->import('vars') if $condition
require strict; strict->import('vars') if $condition
}

This variable was added in Perl 5.003.
Expand Down Expand Up @@ -2461,6 +2424,43 @@ Mnemonic: [ begins subscripts.

Deprecated in Perl v5.12.0.

=item ${^ENCODING}
X<${^ENCODING}>

This variable is no longer supported.

It used to hold the I<object reference> to the C<Encode> object that was
used to convert the source code to Unicode.

Its purpose was to allow your non-ASCII Perl
scripts not to have to be written in UTF-8; this was
useful before editors that worked on UTF-8 encoded text were common, but
that was long ago. It caused problems, such as affecting the operation
of other modules that weren't expecting it, causing general mayhem.

If you need something like this functionality, it is recommended that use
you a simple source filter, such as L<Filter::Encoding>.

If you are coming here because code of yours is being adversely affected
by someone's use of this variable, you can usually work around it by
doing this:

local ${^ENCODING};

near the beginning of the functions that are getting broken. This
undefines the variable during the scope of execution of the including
function.

This variable was added in Perl 5.8.2 and removed in 5.26.0.
Setting it to anything other than C<undef> was made fatal in Perl 5.28.0.

=item ${^WIN32_SLOPPY_STAT}
X<${^WIN32_SLOPPY_STAT}> X<sitecustomize> X<sitecustomize.pl>

This variable no longer has any function.

This variable was added in Perl v5.10.0 and removed in Perl v5.34.0.

=back

=cut

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