package re;$VERSION = 0.02;=head1 NAMEre - Perl pragma to alter regular expression behaviour=head1 SYNOPSIS    use re 'taint';    ($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 $^X in these examples because it's tainted by default.)=head1 DESCRIPTIONWhen C<use re 'taint'> is in effect, and a tainted string is the targetof a regex, the regex memories (or values returned by the m// operatorin list context) are tainted.  This feature is useful when regex operationson tainted data aren't meant to extract safe substrings, but to performother transformations.When C<use re 'eval'> is in effect, a regex is allowed to containC<(?{ ... })> zero-width assertions even if regular expression containsvariable interpolation.  That is normally disallowed, since it is a potential security risk.  Note that this pragma is ignored when the regularexpression is obtained from tainted data, i.e.  evaluation is alwaysdisallowed with tainted regular expresssions.  See L<perlre/(?{ code })>.For the purpose of this pragma, interpolation of precompiled regular expressions (i.e., the result of C<qr//>) is I<not> considered variableinterpolation.  Thus:    /foo${pat}bar/I<is> allowed if $pat is a precompiled regular expression, even if $pat contains C<(?{ ... })> assertions.When C<use re 'debug'> is in effect, perl emits debugging messages when compiling and using regular expressions.  The output is the same as thatobtained by running a C<-DDEBUGGING>-enabled perl interpreter with theB<-Dr> switch. It may be quite voluminous depending on the complexityof the match.  Using C<debugcolor> instead of C<debug> enables aform of output that can be used to get a colorful display on terminalsthat understand termcap color sequences.  Set C<$ENV{PERL_RE_TC}> to acomma-separated list of C<termcap> properties to use for highlightingstrings 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 theother 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,eval	=> 0x00200000,);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;      }      $bits |= $bitmask{$s} || 0;    }    $bits;}sub import {    shift;    $^H |= bits(1,@_);}sub unimport {    shift;    $^H &= ~ bits(0,@_);}1;