On version 1.2.0.212 the following regex will not match the text "Subject":

(Subject)

But this will match:

((?i)Subject)

If there is a capital letter in the regex, (?i) must be used to detect even an exact match in the text.  If the regex is in all lowercase, it will match regardless of the case of the text even without (?i).  If case sensitivity is explicitly turned on with (?-i) and the regex is in uppercase, it will not detect even an exact match in the text:

((?-i)SUBJECT)

does not match "SUBJECT" in the text.

I hope I'm making sense...

Thanks

You can prefix any of the modifiers with a - to do the opposite, so (?i) makes it case insensitive and (?-i) makes it case sensitive.