Re: how to compare column 1 to column 2 and vice versa from multiple rows.

Something like this:

my %seen;

while (my $line = <>) {

    chomp $line;

    print $line
        if $seen{ join '', sort split /\s+/, $line }++;

}
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Use a hash to check for duplicates. Compose a key for the hash in such a way that rows having similar columns give same keys.

Update: Missed ++ has been added.