The pattern you have listed would only match once as it is. The reason is the .* which would match everything past the <b> and then backtrack until it found a </b>. which in the scheme of things is probably not what you want. So even a line like:

<b>this is something</b><b>this is something else</b>
[download]

the $1 would match this is something</b><b>this is something else

what you probably want is to add a .*? instead of .* which would lazily match up to the first </b> I know this isn't quite the answer you were looking for, but thought it deserved mentioning.

-enlil