@array  = glob(*.old);
while(<@array>) {
 $newext = $_; $newext =~ s/old/new/;
 rename($_, $newext);
}
[download]

I think I have this pretty short, however, I've learned that often there are shorter and easier ways to do something. If anyone can point out a shorter path to the goal I seek, it would be appreciated.

humbly -c