Do you know that the WAV file contains only one RIFF chunk?

I am not certain about this. I handled a few sample file with WaveMP3, and it removed more than just 20 bytes from some of the files, but I can't remember how much exactly.

The grep you proposed returns two matches on each file, one beeing "WAVEfmt " and one being "data".

Regarding the OS: The files reside on a Linux (SAMBA) file server, while I usually use Windows for most other things (well: eMail, Office (though, ironically, mostly LaTeX), webbrowsing etc.) because my notebook doesn't run too well under Linux and I don't have the time to find out why. So basically, both Windows and Linux could be used for this task. And Perl is available on both systems, perl 5.6.1 in both cases.

cu,
sven