From my experience, Audio::DSP works fine, but I never really tested it for memory leakage. You could just use the alsa c utilities and call them from Perl, arecord, and aplay. There are others to use too, like sox.

See Tk-applause-meter and look at using mplayer for recording, see ztk-v4l-video-bloger/recorder for some ideas.

Remember, Perl is not fast enough to give you a nice realtime sound spectrum, you will need to fork that off to other c programs, for acceptable performance.