Greetings!

I'm attempting to check an URL with a regexp on whether or not it matches certain criteria (that is, an extremely strict check that is supposed to only let particular URLs pass and reject the rest). However, for some reason it doesn't work as expected.

Here's the code sample in question:

#!/usr/bin/perl -w

use strict;

my $referrer = 'https://www.robidu.de/';

if($referrer =~ /^https?:\/\/(?!www\.)robidu\.de\//)
  {
  print "Match!\n";
  }
else
  { 
  print "No match!\n";
  }

[download]

The URL as given in this sample correctly causes a nonmatch. Removing "www." from the URL in turn correctly gives a match of the regexp.

However, when the "www." in the example is replaced by, for example, "forum." and the check run again, it indicates a nonmatch (and subsequently lets the URL pass) instead of matching and thereby rejecting it.

So what could possibly be going wrong here? Any help would be greatly appreciated.

In reply to regexp: Mind-boggling negative assertions... by Robidu

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.