Text_Soundex
Text::Soundex - Implementation of the Soundex Algorithm as Described by Knuth
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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';
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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 $soundex_nocode.
In scalar context soundex returns the soundex code of its first
argument, and in array context a list is returned in which each element is the
soundex code for the corresponding argument passed to soundex e.g.
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@codes = soundex qw(Mike Stok);
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leaves @codes containing ('M200', 'S320').
Knuth's examples of various names and the soundex codes they map to
are listed below:
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Euler, Ellery -> E460
Gauss, Ghosh -> G200
Hilbert, Heilbronn -> H416
Knuth, Kant -> K530
Lloyd, Ladd -> L300
Lukasiewicz, Lissajous -> L222
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so:
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$code = soundex 'Knuth'; # $code contains 'K530'
@list = soundex qw(Lloyd Gauss); # @list contains 'L300', 'G200'
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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.