re - Perl pragma to alter regular expression behaviour
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'; /^(.*)$/s; # output debugging info # during compile and run time
(We use $^X in these examples because it's tainted by default.)
When use re 'taint' is in effect, and a tainted string is the target of a regex, the regex memories (or values returned by the m// operator in list context) are tainted. This feature is useful when regex operations on tainted data aren't meant to extract safe substrings, but to perform other transformations.
use re 'taint'
When use re 'eval' is in effect, a regex is allowed to contain (?{ ... }) zero-width assertions even if regular expression contains variable interpolation. That is normally disallowed, since it is a potential security risk. Note that this pragma is ignored when the regular expression is obtained from tainted data, i.e. evaluation is always disallowed with tainted regular expresssions. See "(?{ code })" in perlre.
use re 'eval'
(?{ ... })
For the purpose of this pragma, interpolation of preexisting regular expressions is not considered a variable interpolation, thus
/foo${pat}bar/
is allowed if $pat is a preexisting regular expressions, 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. See "Debugging regular expressions" in perldebug for additional info.
use re 'debug'
-DDEBUGGING
The directive use re 'debug' is not lexically scoped. It has both compile-time and run-time effects.
See "Pragmatic Modules" in perlmodlib.
To install lib, copy and paste the appropriate command in to your terminal.
cpanm
cpanm lib
CPAN shell
perl -MCPAN -e shell install lib
For more information on module installation, please visit the detailed CPAN module installation guide.