#!/usr/bin/perl

use strict;
use warnings;

my @array = ( [1..3],['a'..'b'],['A'..'C'] );

my @prev_value;
nested_for(
  sub {
    if (@prev_value) {
      my $diff;
      for (0..$#prev_value) {
        if ($prev_value[$_] ne $_[$_]) {
          $diff = $_;
          last;
        }
      }
      if (defined $diff) {
        for (reverse $diff..$#prev_value) {
          print " ", @prev_value[0..$_];
        }
        print "\n";
      } else {
        print " ";
      }
    }
    print @_;
    @prev_value = @_[0..$#_-1];
  }, reverse @array);

sub nested_for {
  ret_iter(@_)->();
}

sub ret_iter {
  my $fn = shift;
  my $range = shift;
  my $sub = sub { $fn->(@_, $_) for @$range };
  return @_ ? ret_iter($sub, @_) : $sub;
}