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

for my $i ( 0 .. 9 )
    {
    for my $j ( 0 .. 9 )
        {
        for my $k ( 0 .. 9 )
            {
            for my $l ( 0 .. 9 )
                {
                # do something with $i$j$k$l
                }
            }
        }
    }