There is a line:
uid = new_tracks_player84 & comment = file name & st = / design / images / audio30-856.txt & file = / vardata / modules / musicdb / samples / 201209 / d52d5cdf039d23b25f8af73e0b7b5504.mp3 & auto = play
As in Java using a regular expression, pull out:
/vardata/modules/musicdb/samples/201209/d52d5cdf039d23b25f8af73e0b7b5504.mp3 those. value between file = and &