I'm tinkering with my personal website and have a CGI which reads in a real system directory structure to represent categories etc. The resulting hash represents the directory structure plus stores a small amount of info for particular files.

The structure looks like this as a cut-down example, it could be nested to any level, not just what is shown: 

$VAR1 = {
  'misc' => {},
  'docs' => {
    'howtos' => {
      'email' => {
        'index.html' => {
          'date' => '21-1-2004',
          'size' => '691'
        }
      },
      'ftp' => {},
      'ssh' => {}
    }
  }
};

[download]

What I want to do is directly reference one of the nested hashes based on a single string containing the real system path. If I had the string: "/docs/howtos/email/" I'd want to produce the contents of: $VAR1->{docs}->{howtos}->{email}

I came up with a seemingly dodgy way with eval as follows (this is the first time I've used eval before BTW): 

# yes, I realise there is NO error checking :)
# assume $tree contains data structure shown above
# assume input = "/docs/howtos/email/"

my $string = join('}->{',split(/\//,$input));
$string =~ s/^.(.+)/$1}/;
$string = '$tree'.$string."->{'index.html'}->{size};";

# string now contains: "$tree->{docs}->{howtos}->{email}->{'index.html
+'}->{size};"

# constructed reference
print eval $string;

# explicit reference
print $tree->{docs}->{howtos}->{email}->{'index.html'}->{size};

[download]

This outputs the same for both cases and does what I want - but it seems like a hack. I was curious as to how others would do it, and most probably how I *should* do it? :)

Thanks,

Ryan

In reply to Building dynamic nested hash references by ryan

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