RegEx process filtering does not act as intended

[Bidthedog]

Whilst using the current release (2.3.3) I observed that the regular expression filtering does not work as intended - the tests that exist pass, but the implementation was checking the filter on every key press. The first keypress seemed to filter correctly, then subsequent ones failed.

I have forked and will create a PR.

[kasajian]

See https://github.com/Code52/carnac/pull/321