select 'word.01234' ~ E'(?x)
                        ^                # begin-of-string 
                            word         #   root word
                            [.]          #   dot
                            [[:digit:]]+ #   digits...
                        $                # end-of-string
                     '
;

-- caveat:
--   the (?x) option overrides any previously determined
--   options including RE flavor and case sensitivity.