lookarounds do not advance the search

very rudimentary mistake, sorry. (lookarounds are very fun to me but they also bend my head in knots.)
And this could be done a different way... if only look
behind allowed variable-length strings. Fortunately, you can use the curly-bracket repeater for a finite variable-length string, but only in
http://calibre-ebook.com's
editor.
Code:
(?<=>[^<]{,99999})[a-zA-Z]\.[a-zA-Z]
Sigil doesn't use python's regex engine, so this doesn't work.
In Sigil, you can use:
Code:
(>[^<]*?)[a-zA-Z]\.[a-zA-Z]
And it will also capture the part from the preceding tag. However, it is captured and you can replace with "\1" followed by the replacement for the "x.y".