require 'ostruct'

not_in_locals = "we don't want this"
locals = {a: 1, b: 2}
my_binding = OpenStruct.new(locals).instance_eval { binding }
p my_binding
p eval("a", my_binding) #good, we want this
p eval("b", my_binding) #good, we want this
p eval("not_in_locals", my_binding) #bad, don't want it to access this, but it can

ruby binding_of_hash.rb
foo = foo value
baz = 42
binding_of_hash.rb:10:in `eval': undefined local variable or method `not_in_hash' for #<HashBinding:0x007fcc0b9ec1e8> (NameError)
    from binding_of_hash.rb:10:in `eval'
    from binding_of_hash.rb:10:in `evaluate'
    from binding_of_hash.rb:20:in `<main>'