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Text::Soundex(3)


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 Phillips ("ian@pipex.net") and Rich Pinder
  ("rpinder@hsc.usc.edu") supplied ideas and spotted mistakes.

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