I'm on mIRC v7.67, Windows 10 64bit.
when using anchors "^" "$" in multi-line mode, the anchors change from start/end of string, to start/end of line. In the example below, "$" is still treated as end of string, but "^" behaves correctly, both these expressions should pass, the first fails, the second passes.
//var %str = $+(abc,$crlf,def,$crlf,ghi) , %pat1 = /^def$/m , %pat2 = /^ghi$/m | echo -a $regex(%str,%pat1) vs $regex(%str,%pat2)