I am looking to perform a search where a string(bar) is not preceeded immediately by any of the two strings (foo) or (boo)

for example

`foo=bar` should not match

`foo=baz bar` should match

`bar` should match

`boo=bar` should not match

I think the look behind regex would have been perfect for this. However I get an unhandled exception when i try to use `(?<!` from MSVC++ for the look behind

Is the assertion supported in the ? Is it syntactically different? Or can somebody please help me write this regex or emulate the behavior?