print "$_: ", m[^\w+(?:\.\w+)*$] ? "matched\n" : "failed\n"
     for qw[ one one.two one.two.three four.five.six.seven one. one-two ];;
one:  matched
one.two:  matched
one.two.three:  matched
four.five.six.seven:  matched
one.:  failed
one-two:  failed