#!/usr/bin/perl -w
use warnings;
use strict;

my %count;
 
while (<DATA>) {
    chomp; 
    my ($x,$y) = split /\s/;
    ($x,$y) = ($y,$x) if ($x gt $y);
    $count{"$x $y"}++;
}

foreach (sort keys %count) {
    print "people with $_: $count{$_}\n";
}


__DATA__
cat dog
cat fish
pig dog
horse fish
pig fish
dog fish
fish cat