tye, I agree that your first regex would work, but I was specifically looking to see if I could use a lookbehind with a string anchor such as '^'. Your second regex, however, leaves me confused:

$test =~ s#
           (?<!       # Negative lookbehind
             .{6}     # Six of any non-newline character
           )
           (?<=       # Positive lookbehind
             [A-Z]{5} # Five caps
           )
           :          # Here's what we're really substituting   
         #:</B>\n<BR><BR>#;x
[download]

In other words, we're going to substitute out a colon, but only if that is preceded by five caps, but only if the five caps in turn are not preceded by six non-newline characters. Is that what you intended? If so, was that intended as a work-around for the '^' anchor? If it was, I see a lot of problems with it.

Regardless, I'm stuck with my original question: can regex string anchors and lookbehinds be combined?

Cheers,
Ovid

Update: tye, read my commentary in addition to the regex comments and you'll see that we agree. My wording may have been odd, but it's there. :)