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Tie::RegexpHash - Use regular expressions as hash keys


  use Tie::RegexpHash;

  my %hash;

  tie %hash, 'Tie::RegexpHash';

  $hash{ qr/^5(\s+|-)?gal(\.|lons?)?/i } = '5-GAL';

  $hash{'5 gal'};     # returns "5-GAL"
  $hash{'5GAL'};      # returns "5-GAL"
  $hash{'5  gallon'}; # also returns "5-GAL"

  my $rehash = Tie::RegexpHash->new();

  $rehash->add( qr/\d+(\.\d+)?/, "contains a number" );
  $rehash->add( qr/s$/,          "ends with an \`s\'" );

  $rehash->match( "foo 123" );  # returns "contains a number"
  $rehash->match( "examples" ); # returns "ends with an `s'"


This module allows one to use regular expressions for hash keys, so that values can be associated with anything that matches the key.

Hashes can be operated on using the standard tied hash interface in Perl, or using an object-oriented interface described below.


  my $obj = Tie::RegexpHash->new()

Creates a new "RegexpHash" (Regular Expression Hash) object.

  $obj->add( $key, $value );

Adds a new key/value pair to the hash. $key can be a Regexp or a string (which is compiled into a Regexp).

If $key is already defined, the value will be changed. If $key matches an existing key (but is not the same), a warning will be shown if warnings are enabled.

  $value = $obj->match( $quasikey );

Returns the value associated with $quasikey. ($quasikey can be a string which matches an existing Regexp or an actual Regexp.) Returns 'undef' if there is no match.

Regexps are matched in the order they are defined.

  if ($obj->match_exists( $quasikey )) ...

Returns a true value if there exists a matching key.

  $value = $obj->remove( $quasikey );

Deletes the key associated with $quasikey. If $quasikey matches an existing key (but is not the same), a warning will be shown.

Returns the value associated with the key.


Removes all key/value pairs.


Robert Rothenberg <rrwo at>


Russell Harrison <rch at> for patches adding support for serialization.

Simon Hanmer <sch at> & Bart Vetters <robartes at nirya.eb> for pointing out a bug in the logic of the _find() routine in v0.10


Copyright (c) 2001-2002, 2005-2006 Robert Rothenberg. All rights reserved.

Portions Copyright (c) 2006 Russell Harrison. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


Tie::Hash::Regex is a module with a complimentary function. Rather than a hash with Regexps as keys that match against fetches, it has standard keys that are matched by Regexps in fetches.

Regexp::Match::Any matches many Regexps against a variable.

Regexp::Match::List is similar, but supports callbacks and various optimizations.