Negative lookahead does not work for "+" even though works for "@"
I'll attach a test program that shows the effect. Basically, if I have a negative lookahead in the regex like (?!@) and "@" shows up in the proper location I get a mismatch (1. case). This is expected. If I exchange the "@" with a "+" or "[+]" in the regex and a "+" in the input, a match occurs (case 2 and 3). This is the bug. If the "+" or "@" is removed from the string an expected match occurs (case 4 and 5). I was not able to boil this down to a smaller example yet.