Look ahead Positive(?=) Find expression A where expression B follows A(?=B) ...

Atomic Groups are non-capturing and once a match is made will exit the atomic group and throw away all backtracks. Use Atomic Groups for optimising performance. A non-atomic expression \b(foobar|foot|foo)\b and a test string of foots will: match foo of foobar => fail and backtrack to the 2nd alter...

This regexp is used in the SPIP cms for create tags fastly when you are writting a post.

Extract the server and database name from SQL Server connection string

Match lines with CR (Carriege Return) with no LF (Line Feed - New Line) or PG (Page Break) next to it.

Find label in MIPS assembly

It won't capture in the group.we can't back refrence A(?:nt|pple)\sA\1

is just the format for the property control number on the Palm Beach County Florida

kust like [*]

https://msdn.microsoft.com/en-us/library/windows/desktop/aa379649%28v=vs.85%29.aspx S-1-5-32-552 #The built-in system domain. S-1-5-21-109736768-1684412531-2440353719-701 # SIDS are not unique.

shows regular expression