Rolling a die

start:        die  /^\Z/         {$item [1]}

die:          'd' number         {1 + int rand $item [2]}
            | number 'd' number  {my $s = 0;
                                  foreach (1 .. $item [1]) {
                                     $s += 1 + int rand $item [3]
                                  }
                                  $s}

number:       /\d+/

In [1] := d3
Out [1] = 1
In [2] := d3
Out [2] = 2
In [3] := 2d4
Out [3] = 4
In [4] := 3 d  5
Out [4] = 7
In [5] := 3d5
Out [5] = 8
In [6] := foo
Out [6] = <<UNDEF>>