I *think* the problem is that Devel::Peek is writing directly to the C file descriptor 2 (see perlfuc:fileno) rather than via a perl file handle, which basicaly means that any attempt to capture its output via tie is simply bypassed. Ie. The tie magic only works when you use the filehandle, which the perl internals don't.

Update: Forget the rest of this, it's bo..er..wrong! It couldn't work.

I have a feeling that it may be possible to capture the output by dupping the file descriptor. POSIX::dup2 might be one way, and re-opening files(dups) using the "&=2" version of the syntax might be another. I have had a play with the latter, without success, but I didn't spend much time on it.