Hackety hack
Hackety hack, repass all tests
Implement hash clauses: allowed_keys, forbidden_keys
Remove boring _debug_ccl_note, they will be set anyway in add_ccl()
Implement hash clauses: allowed_keys_re, forbidden_keys_re
Release v0.19
Add POD: Manual::Contributing
Add developer notes about the use of idiom '\!defined(first(CODE, LIST))
Fix stringifying a regex for perl >= 5.14.0
Typo in regex
Implement clause re_keys
Release v0.20
Add some sort() to be more deterministic
Bugfix: Prevent clash of variable '$_' when $dt is also '$_'