#!/usr/bin/perl -wT
use strict;

my %validLanguages = (
                      "de" => "german",
                      "en" => "english",
                      "es" => "spanish",
                      "fr" => "french",
                      "it" => "italian",
                      "ja" => "japanise",
                      "ko" => "korean",
                      "ru" => "russian",
                      "sv" => "WHATS THIS",
                      "zh" => "WHATS THIS",
                      "zh_TW" => "WHATS THIS"
                     );

# test it
for ('dog','cat','de,en','   ',',,,','deensvzh') {
  printf "%-10s %s a list of languages\n",
         "'$_'",
         (isItJustAListOfLanguages($_) ? "is" : "is NOT");
}

sub isItJustAListOfLanguages{
  my $text = shift;
  my @tokens = (keys %validLanguages, '\s',',');
  my $tokenpatt = join('|',@tokens);
  return $text =~ /^($tokenpatt)+$/;
}

__END__

'dog'      is NOT a list of languages
'cat'      is NOT a list of languages
'de,en'    is a list of languages
'   '      is a list of languages
',,,'      is a list of languages
'deensvzh' is a list of languages