Regular Expressions: Nested Matches?

[The_Last_TMNT]

How can I setup a regular expression to replace nested text with replacement text. I can't explain it very well, but say I want to replace [asdf] with <asdf>, and my sample text is:

[asdf]adsfasdf[asdf]adsfadsf[/adsf][/adsf]

I end up with this:

<asdf>adsfasdf[asdf]adsfadsf</adsf>[/adsf]

Or something similiar depending on the modifiers I use.

How can I accomplish replaces like this?

[Weedpacket]

I think on the page in the manual that describes the PCRE syntax there is a reference to recursive patterns.

[The_Last_TMNT]

If you could be more specific, I would appreciate it. I've read the pattern syntax page on recursion three times and just don't get it. Maybe I am slow in the head.