How to reverse column order of a file in Linux from the command line

Question

I have a file named ip-list with two columns:

IP1    Server1
IP2    Server2

And I want to produce:

Answer 1

perl -pi -e 's/^([^\t]+)\t([^\t]+)$/\2\t\1/' yourfile.csv

perl -pi -e 'split("\t"); print "$_[1]\t$_[0]"'

The first one probably works on sed, too.