I've created a program that will parse an HTML file using HTML::Parser and generate a tree structure from it. Here is my current working code.

parsehtml.pl
============

#!/usr/bin/perl

use strict;
use warnings;

use HTML::Parser ();

my $htmltree = [ { tag => 'document', content => [] } ];
my $node = $htmltree->[0]->{content};
my @prevnodes = ($htmltree);

sub start {
  my $tagname = shift;
  my $attr = shift;
  my $newnode = {};

  $newnode->{tag} = $tagname;
  foreach my $key(keys %{$attr}) {
    $newnode->{$key} = $attr->{$key};
  }
  $newnode->{content} = [];
  push @prevnodes, $node;
  push @{$node}, $newnode;
  $node = $newnode->{content};
}

sub end {
  my $tagname = shift;

  $node = pop @prevnodes;
}

sub text {
  my $text = shift;

  chomp $text;
  if($text ne '') {
    push @{$node}, $text;
  }
}

my $p = HTML::Parser->new( api_version => 3,
                           start_h => [\&start, "tagname, attr"],
                           end_h   => [\&end,   "tagname"],
                           text_h  => [\&text,  "dtext"] );

$p->parse_file("test.html");
[download]

test.html
=========

<table id="maintable" width="300">
<tr>
<td width="200">some content</td>
<td width="100">more content</td>
</tr>
</table>
[download]

Now for the next challenge. I need to be able to know where I am in the tree structure for any node that I am in while I am walking it. I will pass along a value via CGI in the form of '0.0.2.1.2' which another script will translate as: '$htmltree->[0]->{content}->[0]->{content}->[2]->{content}->[1]->{content}->[2]'. Using the above code, and the following code I wrote for walking the tree and generating HTML from it, how can I mark each outputted HTML tag with its position in the tree?

sub descend_htmltree {
  my $node = shift;
  my $withclickiness = shift || 0;

  foreach my $tmpnode (@{$node}) {
    if(ref($tmpnode) eq 'HASH') {
      my $nodeid = ""; # Magic code to generate node's position in tre
+e
      $htmloutput .= "<div style='border: thin solid #bbbbbb' onDblCli
+ck=\"alert('you clicked $nodeid')\">" if($withclickiness);
      $htmloutput .= "<$tmpnode->{tag}";
      foreach(keys %{$tmpnode}) {
        $htmloutput .= " $_=\"$tmpnode->{$_}\"" if($_ ne 'tag' && $_ n
+e 'content');
      }
      $htmloutput .= ">";
      descend_htmltree($tmpnode->{content});
      $htmloutput .= "</$tmpnode->{tag}>";
      $htmloutput .= "</div>" if($withclickiness);
    } else {
      $htmloutput .= "$tmpnode";
    }
  }
}

sub htmltree_to_html {
  my $filename = shift || '';
  my $withclickiness = shift || 0;

  descend_htmltree($htmltree->[0]->{content}, $withclickiness);
  if($filename ne '') {
    open HTML, "> $filename" or die "Can't open $filename for HTML out
+put";
    print HTML $htmloutput;
    close HTML;
  }

  return $htmloutput;
}
[download]

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