@A_options = @B_options = @C_options = qw(0 1 2 3 4 5 6 7 8 9);

foreach  my $A (@A_options) {
foreach  my $B (@B_options) {
foreach  my $C (@C_options) {
     print $A . $B . $C . ;\n";
     }
  }
}

##</code><code>##

@A_options = @B_options = @C_options = qw(0 1 2 3 4 5 6 7 8 9);

  NestedLoops(
    [\@A_options,\@B_options,\@C_options],
    sub {print  $_[0] . $_[1] . $_[2] . "\n";}
  );