Dynamically/recursively building hashes in Perl?

Question

I'm quite new to Perl and I'm trying to build a hash recursively and getting nowhere. I tried searching for tutorials to dynamically build hashes, but all I could find were introductory articles about hashes. I would be grateful if you point me towards the right direction or suggest a nice article/tutorial.

I'm trying to read from a file which has paths in the form of

one/two/three
four
five/six/seven/eight

and I want to build a hash like

VAR = {
    one : {
        two : {
            three : ""
        }
    }
    four : ""
    five : {
        six : {
            seven : {
                 eight : ""
            }
        }
    }
}

The script I'm using currently is :

my $finalhash = {}; 
my @input = <>;

sub constructHash {
    my ($hashrf, $line) = @_; 
    @elements = split(/\//, $line);
    if(@elements > 1) {
        $hashrf->{shift @elements} = constructHash($hashrf->{$elements[0]}, @elements ); 
    } else {
        $hashrf->{shift @elements} = ""; 
    }
    return $hashrf;
}

foreach $lines (@input) {
    $finalhash = constructHash($finalhash, $lines);
}

Answer 1

This is a bit far-fetched, but it works:

sub insert {
  my ($ref, $head, @tail) = @_;
  if ( @tail ) { insert( \%{$ref->{$head}}, @tail ) }
  else         {            $ref->{$head} = ''      }
}

my %hash;
chomp and insert \%hash, split( '/', $_ ) while <>;

It relies on autovivification, which is admittedly a bit advanced for a beginner.

What would probably make any answer to your question a bit twisted is that you ask for empty strings in the leaves, which is of a different "type" than the hashes of the nodes, and requires a different dereferencing operation.