I've just learned about these two concepts in more detail. I've always been good with RegEx, and it seems I've never seen the need for these 2 zero width assertions.

I'm pretty sure I'm wrong, but I do not see why these constructs are needed. Consider this example:

Match a 'q' which is not followed by a 'u'.

2 strings will be the input:

Iraq
quit

With negative lookahead, the regex looks like this:

q(?!u)

Without it, it looks like this:

q[^u]

For the given input, both of these regex give the same results (i.e. matching Iraq but not quit) (tested with perl). The same idea applies to lookbehinds.

Am I missing a crucial feature that makes these assertions more valuable than the classic syntax?

regex regex-lookarounds
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