Perl supports negative lookbehing and negative lookahead, filed under EXTENDED CONSTRUCTS of perlreref and Extended Patterns of perlre. Lookbehing is slightly limited in scope (i.e no quantifiers), but lookahead isn't.
Also, in regex, you might be better off stating what you *are* looking for and unless the rest

UPDATE:Fixed perldoc links, thanks kyle!

Software speaks in tongues of man.
Stop saying 'script'. Stop saying 'line-noise'.
We have nothing to lose but our metaphores.

In reply to Re: How can I build regexp with "not" assertion? by Erez
in thread How can I build regexp with "not" assertion? by putnik

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.