--- ERB#def_method(mod, methodname, fname='(ERB)')
    ѴRubyץȤ᥽åɤȤ롣
    Υ⥸塼modǻꤷ᥽å̾methodnameǻꤹ롣
    fnameϥץȤݤΥե̾Ǥ롣˥顼˳롣
    
      erb = ERB.new(script)
      erb.def_method(MyClass, 'foo(bar)', 'foo.erb')

