#! perl -slw
use strict;

sub pairs {
    map {
        my $i = $_;
        map [ @_[ $i, $_ ] ], $i+1 .. $#_;
    } 0 .. $#_;
}

my %pairCounts;

++$pairCounts{ "@$_" } for map pairs( sort split ), <DATA>;

print "@$_" while @{ $_ = [ each %pairCounts ] };


__DATA__
dog monkey cat
cat ball stone
monkey iron cat zoo


##</code><code>##

C:\test>junk4
cat stone 1
cat monkey 2
iron monkey 1
cat zoo 1
dog monkey 1
monkey zoo 1
cat dog 1
ball cat 1
cat iron 1
iron zoo 1
ball stone 1