#!/usr/bin/perl

# https://perlmonks.org/?node_id=1218823

use strict;
use warnings;

my %dups;

local $_ = do { local $/; <DATA> };

/\b(\d+)\b.*?\b(\d+)\b(?{$dups{"$1 $2"}++})(*FAIL)/;

$dups{$_} > 1 and print "$_ repeated $dups{$_} times\n" for sort keys 
+%dups;

__DATA__
1 2 5 9
1 2 5 10
4 5 10 12
5 9 10 11
[download]

Outputs:

1 2 repeated 2 times
1 5 repeated 2 times
2 5 repeated 2 times
5 10 repeated 3 times
5 9 repeated 2 times
[download]