Apache::MP3::L10N is a base class for Apache::MP3 interface localization.
This module is the base class for generating language handles (via Locale::Maketext) which Apache::MP3 (and subclasses) use for presenting their interface.
To localize this for your language of choice, see the source for Apache/L10N/fr.pm for an example lexicon that should contain all the English phrases, and an example French translation.
For example, if you're localizing this to Swahili, you'd copy Apache/L10N/fr.pm to Apache/L10N/sw.pm (since I18N::LangTags::List tells us that sw is the language tag for Swahili), and change its package Apache::MP3::L10N::fr; line to package Apache::MP3::L10N::sw;, and then you'd replace all the French phrases that are the values in %Lexicon with Swahili phrases.
For example, you'd change:
'fetch' => 'sauvegarder',
'fetch' => 'lete',
if you considered "lete" (from the infinitive "kuleta", haul) to be a good translation of the English "fetch" in that context.
Email me (Sean) if you have any questions.