--- throw(tag[, value=nil])

    Ʊ tag ꤷ catch Υ֥å
    ޤ(᥽åɤۤ)æФޤ⤷Ʊ tag 
    ԤäƤ catch ¸ߤʤ NameError 
    åɤλޤtag ʸޤϥܥǤ
    value  catch ͤˤʤޤ

    :

      ret = catch(:exit) {
         throw :exit, 25
         some_process()    # Ф˼¹Ԥʤ
         10
      }
      p ret   #=> 25

