# 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
}