set_trace_func (cont'd)

 1 ["line", "test.rb", 3, nil, #<Binding:0x401b7b74>, false]
 2 ["call", "test.rb", 1, :foo, #<Binding:0x401b7a48>, Object]
 3 ["line", "test.rb", 1, :foo, #<Binding:0x401b7a0c>, Object]
 4 ["c-call", "test.rb", 1, :puts, #<Binding:0x401b7840>, Kernel]
 5 ["c-call", "test.rb", 1, :write, #<Binding:0x401b7804>, IO]
 6 foo!["c-return", "test.rb", 1, :write, #<Binding:0x401b7700>, IO]
 7 ["c-call", "test.rb", 1, :write, #<Binding:0x401b75fc>, IO]
 8 
 9 ["c-return", "test.rb", 1, :write, #<Binding:0x401b750c>, IO]
10 ["c-return", "test.rb", 1, :puts, #<Binding:0x401b741c>, Kernel]
11 ["return", "test.rb", 1, :foo, #<Binding:0x401b732c>, Object]