132 lines
3.9 KiB
Perl
132 lines
3.9 KiB
Perl
package re;
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$VERSION = 0.02;
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=head1 NAME
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re - Perl pragma to alter regular expression behaviour
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=head1 SYNOPSIS
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use re 'taint';
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($x) = ($^X =~ /^(.*)$/s); # $x is tainted here
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$pat = '(?{ $foo = 1 })';
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use re 'eval';
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/foo${pat}bar/; # won't fail (when not under -T switch)
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{
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no re 'taint'; # the default
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($x) = ($^X =~ /^(.*)$/s); # $x is not tainted here
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no re 'eval'; # the default
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/foo${pat}bar/; # disallowed (with or without -T switch)
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}
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use re 'debug'; # NOT lexically scoped (as others are)
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/^(.*)$/s; # output debugging info during
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# compile and run time
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use re 'debugcolor'; # same as 'debug', but with colored output
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...
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(We use $^X in these examples because it's tainted by default.)
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=head1 DESCRIPTION
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When C<use re 'taint'> is in effect, and a tainted string is the target
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of a regex, the regex memories (or values returned by the m// operator
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in list context) are tainted. This feature is useful when regex operations
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on tainted data aren't meant to extract safe substrings, but to perform
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other transformations.
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When C<use re 'eval'> is in effect, a regex is allowed to contain
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C<(?{ ... })> zero-width assertions even if regular expression contains
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variable interpolation. That is normally disallowed, since it is a
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potential security risk. Note that this pragma is ignored when the regular
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expression is obtained from tainted data, i.e. evaluation is always
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disallowed with tainted regular expresssions. See L<perlre/(?{ code })>.
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For the purpose of this pragma, interpolation of precompiled regular
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expressions (i.e., the result of C<qr//>) is I<not> considered variable
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interpolation. Thus:
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/foo${pat}bar/
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I<is> allowed if $pat is a precompiled regular expression, even
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if $pat contains C<(?{ ... })> assertions.
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When C<use re 'debug'> is in effect, perl emits debugging messages when
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compiling and using regular expressions. The output is the same as that
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obtained by running a C<-DDEBUGGING>-enabled perl interpreter with the
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B<-Dr> switch. It may be quite voluminous depending on the complexity
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of the match. Using C<debugcolor> instead of C<debug> enables a
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form of output that can be used to get a colorful display on terminals
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that understand termcap color sequences. Set C<$ENV{PERL_RE_TC}> to a
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comma-separated list of C<termcap> properties to use for highlighting
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strings on/off, pre-point part on/off.
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See L<perldebug/"Debugging regular expressions"> for additional info.
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The directive C<use re 'debug'> is I<not lexically scoped>, as the
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other directives are. It has both compile-time and run-time effects.
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See L<perlmodlib/Pragmatic Modules>.
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=cut
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my %bitmask = (
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taint => 0x00100000,
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eval => 0x00200000,
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);
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sub setcolor {
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eval { # Ignore errors
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require Term::Cap;
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my $terminal = Tgetent Term::Cap ({OSPEED => 9600}); # Avoid warning.
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my $props = $ENV{PERL_RE_TC} || 'md,me,so,se'; # can use us/ue later
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my @props = split /,/, $props;
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$ENV{TERMCAP_COLORS} = join "\t", map {$terminal->Tputs($_,1)} @props;
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};
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not defined $ENV{TERMCAP_COLORS} or ($ENV{TERMCAP_COLORS} =~ tr/\t/\t/) >= 4
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or not defined $ENV{PERL_RE_TC}
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or die "Not enough fields in \$ENV{PERL_RE_TC}=`$ENV{PERL_RE_TC}'";
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}
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sub bits {
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my $on = shift;
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my $bits = 0;
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unless(@_) {
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require Carp;
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Carp::carp("Useless use of \"re\" pragma");
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}
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foreach my $s (@_){
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if ($s eq 'debug' or $s eq 'debugcolor') {
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setcolor() if $s eq 'debugcolor';
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require DynaLoader;
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@ISA = ('DynaLoader');
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bootstrap re;
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install() if $on;
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uninstall() unless $on;
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next;
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}
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$bits |= $bitmask{$s} || 0;
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}
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$bits;
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}
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sub import {
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shift;
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$^H |= bits(1,@_);
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}
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sub unimport {
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shift;
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$^H &= ~ bits(0,@_);
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}
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1;
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