rename linux command

Why have I not found this before....

rename [ -v ] [ -n ] [ -f ] perlexpr [ files ]

-n Test Mode

Lets see what would happen if we issued this command

rename -n 's/tar.tg/tgz/' *.gz

It outputs

rename(000.tar.tg, 000.tgz)
rename(001.tar.tg, 001.tgz)
rename(002.tar.tg, 002.tgz)
rename(003.tar.tg, 003.tgz)