Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth
$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';
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
(how unlikely this is depends on the data set being dealt with.) Any value
can be assigned to
In scalar context
soundex returns the soundex code of its first argument, and in array context a list
is returned in which each element is the soundex code for the corresponding
argument passed to
@codes = soundex qw(Mike Stok);
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
$code = soundex 'Knuth'; # $code contains 'K530' @list = soundex qw(Lloyd Gauss); # @list contains 'L300', 'G200'
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
Heilbronn end up with a soundex code of
This code was implemented by Mike Stok (
email@example.com) from the description given by Knuth. Ian Phillips (
firstname.lastname@example.org) and Rich Pinder (
email@example.com) supplied ideas and spotted mistakes.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.