use strict;
use warnings;
my @array = sort {$a <=> $b} qw/ 23 45 12 4 8 7 5/;

while (my $item = shift @array) {
    print "$item $_\n" for @array;
}

##</code><code>##

4 5
4 7
4 8
4 12
4 23
4 45
5 7
5 8
5 12
5 23
5 45
7 8
7 12
7 23
7 45
8 12
8 23
8 45
12 23
12 45
23 45