/(?:test|spam|xxx| <- one of those, or:
(?:\.|_|-)? <- can begin with . or _ or - but does not have to
(?: ... ) <- huge list of words that can be surrounded by those ._-'s, noteworthy parts are:
germany? <- matches german and germany
fansub(?:bed)? <- matches fansub and fansubbed
(?:swe|nor|pl|kor|cz|nl|sp|fr)(?:(?:s|d)ubs?)? <- example matches: swe, swesub, swesubs, swedub, swedubs; i had a typo here first where there was an additional | after fr: ..|fr|)(..
j(?:a?p|pn) <- matches jp, jpn, jap
(?:\.|_|-)? <- can end with . or _ or - but does not have to