johngg@abouriou ~/perl/Monks $ perl -Mstrict -Mwarnings -E '
for my $w ( 0 .. 6 )
{
    for my $x ( $w + 1 .. 7 )
    {
        for my $y ( $x + 1 .. 8 )
        {
            for my $z ( $y + 1 .. 9 )
            {
                say join q{}, $w, $x, $y, $z;
            }
        }
    }
}' | wc -l
210