--- sub(pattern, replace)
--- sub!(pattern, replace)
--- sub(pattern) {|matched| ... }
--- sub!(pattern) {|matched| ... }

    ʸ pattern ((*ǽ*))ޥåʬ replace 
    ֤ޤ

    ֥åꤷƸƤӽФ줿ˤϡǽ˥ޥåʬ֥
    ɾ֤ͤޤ

    sub ִʸ֤ޤ
    sub!  self ѹ֤ޤִ
    ʤä nil ֤ޤ

    ޥå٤Ԥʤ gsub ƱǤ

    ruby 1.7 feature: 1.6 ϡpattern ʸξ硢
    ʸɽ˥ѥ뤷Ƥޤ1.7 ʹߤϡʸ
    󤽤ΤΤѥˤʤޤ

