the rename command

[Archie Benton]

I'm an ex-redhat/fedora user. The rename command was simple over in
fedora.  When I try to use it in Ubuntu it expects me to enter a perl
expression. I'm not sure I'm ready to learn perl or even "regular
expressions". I'm just trying to rename a bunch of files. For example
let's say I have cow1.txt, cow2.txt and cow3.txt in a subdirectory. I
just want to rename them all to pig1.txt, pig2.txt and pig3.txt. The
man page on the rename command expects me to put a perl expression in.
Ugh. Any way around this? I've tried to "read the man".