You are absolutely right about the punctuation. In my use case it just appears virtually never (unless you test it ;-)

I might consider using a negative lookbehind for punctuation, like so:

use strict;
use warnings;
use Regexp::Common qw/URI/;

my  $text = 'http://perl-6.de/,';

if ($text =~ m/($RE{URI}{HTTP}(?<![.,]))/){
    print "Match: $1\n";
}
__END__
# Output:
Match: http://perl-6.de/
[download]

I think I'll add this to my CGI scripts as soon as I have write access to the repository again.