Thanks for the responses!

JavaFan, you have it there... on the Linux (Ubuntu) box /bin/sh is a symlink to dash which doesn't have brace expansion. I assumed /bin/sh would be a link to bash but it ain't. On the FreeBSD, I thought I was using /bin/sh but actually my user accounts are set to use tcsh.

Perl always calls /bin/sh so that's why brace expansion doesn't work. On both systems Perl is not using a shell that supports it (whereas my terminal sessions are).

Thankyou FunkyMonk for the unlink/glob hint. Looks like a neater, more Perl-ish way of doing what I need so I will look into it.

Thanks again all.