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Text::Soundex(3pm)                    Perl Programmers Reference Guide                    Text::Soundex(3pm)



NAME
       Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth

SYNOPSIS
         use Text::Soundex;

         $code = soundex $string;            # get soundex code for a string
         @codes = soundex @list;             # get list of codes for list of strings

         # set value to be returned for strings without soundex code

         $soundex_nocode = 'Z000';

DESCRIPTION
       This module implements the soundex algorithm as described by Donald Knuth in Volume 3 of The Art of
       Computer Programming.  The algorithm is intended to hash words (in particular surnames) into a small
       space using a simple model which approximates the sound of the word when spoken by an English
       speaker.  Each word is reduced to a four character string, the first character being an upper case
       letter and the remaining three being digits.

       If there is no soundex code representation for a string then the value of $soundex_nocode is
       returned.  This is initially set to "undef", but many people seem to prefer an unlikely value like
       "Z000" (how unlikely this is depends on the data set being dealt with.)  Any value can be assigned to
       $soundex_nocode.

       In scalar context "soundex" returns the soundex code of its first argument, and in list context a
       list is returned in which each element is the soundex code for the corresponding argument passed to
       "soundex" e.g.

         @codes = soundex qw(Mike Stok);

       leaves @codes containing "('M200', 'S320')".

EXAMPLES
       Knuth's examples of various names and the soundex codes they map to are listed below:

         Euler, Ellery -> E460
         Gauss, Ghosh -> G200
         Hilbert, Heilbronn -> H416
         Knuth, Kant -> K530
         Lloyd, Ladd -> L300
         Lukasiewicz, Lissajous -> L222

       so:

         $code = soundex 'Knuth';              # $code contains 'K530'
         @list = soundex qw(Lloyd Gauss);      # @list contains 'L300', 'G200'

LIMITATIONS
       As the soundex algorithm was originally used a long time ago in the US it considers only the English
       alphabet and pronunciation.

       As it is mapping a large space (arbitrary length strings) onto a small space (single letter plus 3
       digits) no inference can be made about the similarity of two strings which end up with the same
       soundex code.  For example, both "Hilbert" and "Heilbronn" end up with a soundex code of "H416".

AUTHOR
       This code was implemented by Mike Stok ("stok@cybercom.net") from the description given by Knuth.
       Ian Phillipps ("ian@pipex.net") and Rich Pinder ("rpinder@hsc.usc.edu") supplied ideas and spotted
       mistakes.



perl v5.8.8                                      2001-09-21                               Text::Soundex(3pm)