|What it does:||don't select this (negative lookahead)|
?! is a bit of regex that will help you select the text ahead of a certain line as long as it doesn't contain what's after the exclamation point.
Imagine you have the word title. If you want to get rid of the second t but not the first, do this:
python replace.py -page:whatever 't(?!i)' ''
This will return tile, having removed only the t that doesn't precede an i.
Note that if you are running your bot through a Unix command line tool, an error message will be thrown if this ?! syntax is used within "double quotes", but will be accepted if the regex is contained within 'single quotes'.