#! /usr/bin/perl -w
use strict;

my @chars
  = ("a".."z", "A".."Z", 0..9
    , split //, qq(!"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~));

my $x = 0;
while (++$x) {
  nested_for(
      sub {print join "", @_, "\n";}
    , map \@chars, 1..$x
  );
}

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;
}