...alll of the above, plus: when you run a cron job it does not usually invoke a login shell. The effect of that is then dependant on which shell you are using, and what is in your startup files. If critical environment variables are set in a startup file then you may find they are not set - PATH is an example and is mentioned above.

I have to say that your 'if' statements are laborious, try using preset hash.
Update:

%languagenames = ("English" => "en",
                  "Indonesian" => "id",
                  "Chinese"    => "zh",
                  "Danish"     => "da",
                  "German"     => "de",
                  "Spanish"    => "es",
                  "Esperanto"  => "eo",
                  "French"     => "fr",
                  "Italian"    => "it"
                  "Creole"     => "cpf",
                  "Dutch"      => "nl",
                  "Norwegian"  => "no",
                  "Polish"     => "pl",
                  "Portuguese" => "pt"
                  "Russian"    => "ru",
                  "Finnish"    => "fi",
                  "Swedish"    => "sv",
                  "Turkish"    => "tr");
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The hash should be global, or a state variable if you have 5.10. Then in the subroutine:

%language = $languagenames{$languagename};
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You can use a simple array for the month numbers.