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package re;
our $VERSION = 0.05;
=head1 NAME
re - Perl pragma to alter regular expression behaviour
=head1 SYNOPSIS
use re 'taint';
($x) = ($^X =~ /^(.*)$/s); # $x is tainted here
$pat = '(?{ $foo = 1 })';
use re 'eval';
/foo${pat}bar/; # won't fail (when not under -T switch)
{
no re 'taint'; # the default
($x) = ($^X =~ /^(.*)$/s); # $x is not tainted here
no re 'eval'; # the default
/foo${pat}bar/; # disallowed (with or without -T switch)
}
use re 'debug'; # NOT lexically scoped (as others are)
/^(.*)$/s; # output debugging info during
# compile and run time
use re 'debugcolor'; # same as 'debug', but with colored output
...
(We use $^X in these examples because it's tainted by default.)
=head1 DESCRIPTION
When C<use re 'taint'> is in effect, and a tainted string is the target
of a regex, the regex memories (or values returned by the m// operator
in list context) are tainted. This feature is useful when regex operations
on tainted data aren't meant to extract safe substrings, but to perform
other transformations.
When C<use re 'eval'> is in effect, a regex is allowed to contain
C<(?{ ... })> zero-width assertions even if regular expression contains
variable interpolation. That is normally disallowed, since it is a
potential security risk. Note that this pragma is ignored when the regular
expression is obtained from tainted data, i.e. evaluation is always
disallowed with tainted regular expressions. See L<perlre/(?{ code })>.
For the purpose of this pragma, interpolation of precompiled regular
expressions (i.e., the result of C<qr//>) is I<not> considered variable
interpolation. Thus:
/foo${pat}bar/
I<is> allowed if $pat is a precompiled regular expression, even
if $pat contains C<(?{ ... })> assertions.
When C<use re 'debug'> is in effect, perl emits debugging messages when
compiling and using regular expressions. The output is the same as that
obtained by running a C<-DDEBUGGING>-enabled perl interpreter with the
B<-Dr> switch. It may be quite voluminous depending on the complexity
of the match. Using C<debugcolor> instead of C<debug> enables a
form of output that can be used to get a colorful display on terminals
that understand termcap color sequences. Set C<$ENV{PERL_RE_TC}> to a
comma-separated list of C<termcap> properties to use for highlighting
strings on/off, pre-point part on/off.
See L<perldebug/"Debugging regular expressions"> for additional info.
The directive C<use re 'debug'> is I<not lexically scoped>, as the
other directives are. It has both compile-time and run-time effects.
See L<perlmodlib/Pragmatic Modules>.
=cut
# N.B. File::Basename contains a literal for 'taint' as a fallback. If
# taint is changed here, File::Basename must be updated as well.
my %bitmask = (
taint => 0x00100000, # HINT_RE_TAINT
eval => 0x00200000, # HINT_RE_EVAL
);
sub setcolor {
eval { # Ignore errors
require Term::Cap;
my $terminal = Tgetent Term::Cap ({OSPEED => 9600}); # Avoid warning.
my $props = $ENV{PERL_RE_TC} || 'md,me,so,se,us,ue';
my @props = split /,/, $props;
my $colors = join "\t", map {$terminal->Tputs($_,1)} @props;
$colors =~ s/\0//g;
$ENV{PERL_RE_COLORS} = $colors;
};
}
sub bits {
my $on = shift;
my $bits = 0;
unless (@_) {
require Carp;
Carp::carp("Useless use of \"re\" pragma");
}
foreach my $s (@_){
if ($s eq 'debug' or $s eq 'debugcolor') {
setcolor() if $s eq 'debugcolor';
require XSLoader;
XSLoader::load('re');
install() if $on;
uninstall() unless $on;
next;
}
if (exists $bitmask{$s}) {
$bits |= $bitmask{$s};
} else {
require Carp;
Carp::carp("Unknown \"re\" subpragma '$s' (known ones are: @{[join(', ', map {qq('$_')} 'debug', 'debugcolor', sort keys %bitmask)]})");
}
}
$bits;
}
sub import {
shift;
$^H |= bits(1, @_);
}
sub unimport {
shift;
$^H &= ~ bits(0, @_);
}
1;
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