It's easier for audio pro's to analyze an audio file in advance, like with Cooledit (Audition), Sonic Foundry, Live or any other equivalent to view it's waveform. Out of such waveform you could find the bpm, loop points, how heavy compressed the audio is, even if it's ambient or techno. Examples of such waveform could be found at http://images.google.be/images?q=audio+waveform

I'd only visualize the waveform as it's pure form in a 400x80.png box for example; although other operations like FFT form etc are always welcome too, for those who need that more...

I'd say Perl is mature enough to process such information flawless although I'm unable to find any links ...