Re: Ensuring HTML is "balanced"

HTML::Treebuilder is a good answer. It is pretty tolerant of missing close tags and can generate nice HTML output if you ask it nicely. You may also be interested in HTML::Lint which parses HTML and generates an error report.

use strict;
use warnings;
use HTML::TreeBuilder;
use HTML::Lint;

my $html = do {local $/; (<DATA>)};

my $lint = HTML::Lint->new (only_types => HTML::Lint::Error::STRUCTURE
+);

$lint->parse ($html);
$lint->eof ();

print "HTML::Lint report:\n";
print join "\n", map {$_->as_string ()} $lint->errors ();

my $tree = HTML::TreeBuilder->new ();

$tree->parse ($html);
$tree->eof ();

print "\n\nTreeBuilder cleaned up HTML\n";
print $tree->as_HTML ();

__DATA__
<p><b><i>test</b></p>
[download]

Prints:

HTML::Lint report:
 (1:14) <i> at (1:7) is never closed
 (1:18) <body> tag is required
 (1:18) <head> tag is required
 (1:18) <html> tag is required
 (1:18) <title> tag is required

TreeBuilder cleaned up HTML
<html><head></head><body><p><b><i>test</i></b></body></html>
[download]

DWIM is Perl's answer to Gödel

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Re^2: Ensuring HTML is "balanced" by Anonymous Monk on Mar 25, 2008 at 19:03 UTC
...So since the cleaned up HTML in fact has a broken p tag, are we free to assume that the Lint report and Treebuilder handle P tags in an amusing manner?	[reply]
Re^3: Ensuring HTML is "balanced" by GrandFather (Saint) on Mar 26, 2008 at 01:45 UTC
Actually HTML doesn't require that some tags (including p tags) be closed. In particular the HTML 4.01 specification in section 9.3.1 says: Paragraphs: the P element Start tag: required, End tag: optional so strictly speaking the p tag is not broken. Perl is environmentally friendly - it saves trees	[reply]
Re^3: Ensuring HTML is "balanced" by ww (Archbishop) on Mar 26, 2008 at 00:47 UTC
This is a common misconception (and one which I think reflects what the standard SHOULD be). Even though the close `</p>` tag is mandatory for certain other standards, `</p>` is optional in html 4.01, per http://www.w3.org/TR/html401/struct/text.htm and other w3c references: 9.3.1 Paragraphs: the P element ... Start tag: required, End tag: optional Whether or not this stands in the forthcoming html 5.0 standard is unknown.	[reply]