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Technical Overview
  internal package Foswiki::Plurals  
Handle conversion of plural topic names to singular form.
Try to singularise plural topic name. 
-  $web- the web the topic must be in
-  $pluralForm- topic name
 
Returns undef if no singular form exists, otherwise returns the
singular form of the topic
I18N - Only apply plural processing if site language is English, or
if a built-in English-language web.  Plurals
apply to names ending in 's', where topic doesn't exist with plural
name.
Note that this is highly langauge specific, and need to be enabled
on a per-installation basis with $Foswiki::cfg{PluralToSingular}.