PERIOD (.) - the period is used to show a final end to the thought/sentence and indeed verse; after an abbreviation. The reader will most likely stop to think about what has been read so far.
COMMA (,) - the comma is used to show a separation of ideas or elements within the verse. In a poem, you can also use it to eliminate excess words. Eg "The sun, rain, road flogged him to death" eliminating 'and the' twice. It is also used to separate two or more complete, independent clauses in a verse:
SEMICOLON (;) - the semicolon is used to connect two independent clauses in a verse or at the end of a verse (linking two verses):