#!/usr/bin/perl
use strict;
use warnings;
use 5.010;

my @list = qw(PA5098  PA5100  PA5092  PA3175);

for (my $i = 0; $i < @list - 1;  $i++) {
    for (my $j = $i + 1; $j < @list;  $j++) {
        my $diff = $j - $i;
        print "$list[$i] $list[$j] $diff\n";
    }
}