#!/usr/bin/perl -lan # Usage: thisscript.pl genes.txt # %seen is a hash where we store keys composed from seen rows # @F is an array of 2 elements $F[0] is a first column of your file and $F[1] is the second one (see [doc://perlrun] -a switch # So the key for row is composed by concatenation of sorted columns if ( $seen{ join ' ', sort @F }++ ) { # %uniq hash will keep seen columns first and second $uniq{$F[0]}++; $uniq{$F[1]}++; } # the code above is loops over each row of file because of -n switch see [doc://perlrun] END { # this block run just before exit print for keys %uniq; }