--- eval(expr[, binding[, fname[, lineno=1]]])

    ʸ expr  Ruby ץȤɾƤη̤֤
    2 Proc ֥Ȥޤ Binding ֥
    ȤͿ硢Υ֥ȤƥȤʸ
    ɾޤbinding ⻲ȤƤ

        def foo
          a = 1
          binding
        end

        eval("p a", foo)  # => 1

    fname  lineno Ϳ줿ˤϡե
    fname ֹ lineno ʸ󤬤뤫Τ褦
    ѥ뤵졢åȥ졼ɽʤɤ򺹤ؤ뤳Ȥ
    Ǥޤ

