This matches "regular" HTML tags -- the part that matches the element may need to be changed slightly, but other than that, it matches: <ELEMENT ( ATTR ( = VALUE )? )* >. 
my $open = qr{
  < [a-zA-Z][a-zA-Z0-9]*
  (?:
    \s+ \w+
    (?: \s* = \s*
      (?: "[^"]*" | '[^']*' | [^\s>]* )
    )?
  )*
  \s*
  >
}x;

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The closing tags are far simpler: 
my $close = qr{
  < / \s* [a-zA-Z][a-zA-Z0-9]* \s* >
}x;

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Comments are slightly trickier: 
# the following are comments:
# <!-- ab -- cd -->   <!-- ab -->    <!---->
# <!-- ab -- cd -- >  <!-- ab -- >   <!---- >

my $comment = qr{
  <!--              # <!--
  [^-]*             # 0 or more non -'s
  (?:               
    (?! -- \s* > )    # that's not --, space, then >
    -                 # a -
    [^-]*             # 0 or more non -'s
  )*                # 0 or more times
  -- \s* >          # --, space, then >
}x;

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The DTD tag is more difficult. There are specific classes of DTD tags (see the specs). So right onw I don't have a regex to handle them. But combining the other three regexes: 
while ($HTML =~ /\G($open|$close|$comment|[^<]+)/g) {
  # do something with $1
}

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Now, using this to create a tree structure of an HTML file shouldn't be too complicated, especially if we use a nice trick like: 
# requires the (?{...}) structure
use re 'eval';

while ($HTML =~ m{
  \G
  (
    $open    (?{ $STATE = 'open'    }) |
    $close   (?{ $STATE = 'close'   }) |
    $comment (?{ $STATE = 'comment' }) |
    [^<]+    (?{ $STATE = 'TEXT'    })
  )
}xg) {
  # do something with $1 and $STATE
}

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And you can modify $open and $close to keep track of the element name by putting parens in there.

It's a matter of thoroughness.

japhy -- Perl and Regex Hacker

In reply to Re: Re (tilly) 2: HTML Matching by japhy
in thread HTML Matching by spaz

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