Algorithm::Loops' NestedLoops allows a non-recursive implementation:
use Algorithm::Loops 'NestedLoops';
sub find_path {
my ($adj_list, $length) = @_;
my %been_there;
NestedLoops([
[sort {$a <=> $b} keys %$adj_list],
(sub {
# The last value on @_ has just changed, so remove it from %be
+en_there
# and set the new one
my ($last_position, $last_value) = ($#_, $_[-1]);
delete $been_there{$_} for grep $been_there{$_} >= $last_posit
+ion, keys %been_there;
$been_there{$last_value} = $last_position;
# Here I grep out the already-visited nodes, but you could als
+o exclude
# any letters that don't result in prefixes of real words.
[ grep !defined($been_there{$_}), @{$adj_list->{$last_value}}
+]
}) x ($length-1)]
);
}
my $i = find_path(\%adjacency_list, 3);
my @path;
print "@path\n" while @path = $i->();
Caution: Contents may have been coded under pressure.