use YAPE::Regex::Explain;
print  YAPE::Regex::Explain->new(qr(<!--[^-]+-->) )->explain();
__END__
The regular expression:

(?-imsx:<!--[^-]+-->)

matches as follows:

NODE         EXPLANATION
----------------------------------------------------------
(?-imsx:     group, but do not capture (case-sensitive)
             (with ^ and $ matching normally) (with . not
             matching \n) (matching whitespace and #
             normally):
----------------------------------------------------------
  <!--         '<!--'
----------------------------------------------------------
  [^-]+        any character except: '-' (1 or more times
               (matching the most amount possible))
----------------------------------------------------------
  -->          '-->'
----------------------------------------------------------
)            end of grouping
----------------------------------------------------------

##</code><code>##

$ perl -le '$_="<!--rm me--><p>good</p><!--rm-too-->";s/<!--[^-]+-->//g;print'
<p>good</p><!--rm-too-->