for my $a1 (@x) {
    for my $a2 (@$a1) {
        for my $a3 (@$a2) {
            ... # hope you get the pattern by now
        }          
    }        
}
[download]

For covering arbitrary depth of nesting you could apply a recursive function (a so called "walker")

If the elements are other than array_refs you might want to add cases after testing ref $aX.