Re man page on AIX

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re(3)		       Perl Programmers Reference Guide			 re(3)

NAME
       re - Perl pragma to alter regular expression behaviour

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.)

DESCRIPTION
       When "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 opera‐
       tions on tainted data aren't meant to extract safe substrings, but to
       perform other transformations.

       When "use re 'eval'" is in effect, a regex is allowed to contain "(?{
       ... })" zero-width assertions even if regular expression contains vari‐
       able interpolation.  That is normally disallowed, since it is a poten‐
       tial 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 "(?{ code })" in
       perlre.

       For the purpose of this pragma, interpolation of precompiled regular
       expressions (i.e., the result of "qr//") is not considered variable
       interpolation.  Thus:

	   /foo${pat}bar/

       is allowed if $pat is a precompiled regular expression, even if $pat
       contains "(?{ ... })" assertions.

       When "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 "-DDEBUGGING"-enabled perl interpreter with
       the -Dr switch. It may be quite voluminous depending on the complexity
       of the match.  Using "debugcolor" instead of "debug" enables a form of
       output that can be used to get a colorful display on terminals that
       understand termcap color sequences.  Set $ENV{PERL_RE_TC} to a comma-
       separated list of "termcap" properties to use for highlighting strings
       on/off, pre-point part on/off.  See "Debugging regular expressions" in
       perldebug for additional info.

       The directive "use re 'debug'" is not lexically scoped, as the other
       directives are.	It has both compile-time and run-time effects.

       See "Pragmatic Modules" in perlmodlib.

perl v5.8.8			  2008-09-19				 re(3)
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