use Algorithm::Loops 'NestedLoops';

my %pat = (
  L => ['a' .. 'z'],
  N => [0 .. 9]
);

my $pattern = shift || "LLN";

NestedLoops(
  [ @pat{ split //, $pattern } ],
  sub { print join("", @_), $/ }
);

##</code><code>##

my %pat = (
  L => ['a' .. 'z'],
  N => [0 .. 9]
);

my $pattern = shift || "LLN";

$_ = sprintf "{%s}", join ",", @$_
  for values %pat;

my $glob = join "", @pat{ split //, $pattern };
print "$_\n" for glob($glob);