disasm

>> puts RubyVM::InstructionSequence.compile('-2 ** 2').disasm
== disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(1,7)> (catch: FALSE)
0000 putobject                              2                         (   1)[Li]
0002 putobject                              2
0004 opt_send_without_block                 <calldata!mid:**, argc:1, ARGS_SIMPLE>
0006 opt_send_without_block                 <calldata!mid:-@, argc:0, ARGS_SIMPLE>
0008 leave
=> nil
>> puts RubyVM::InstructionSequence.compile('-2.itself ** 2').disasm 
== disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(1,14)> (catch: FALSE)
0000 putobject                              -2                        (   1)[Li]
0002 opt_send_without_block                 <calldata!mid:itself, argc:0, ARGS_SIMPLE>
0004 putobject                              2
0006 opt_send_without_block                 <calldata!mid:**, argc:1, ARGS_SIMPLE>
0008 leave
=> nil
>> puts RubyVM::InstructionSequence.compile('-(2.itself) ** 2').disasm 
== disasm: #<ISeq:<compiled>@<compiled>:1 (1,0)-(1,16)> (catch: FALSE)
0000 putobject                              2                         (   1)[Li]
0002 opt_send_without_block                 <calldata!mid:itself, argc:0, ARGS_SIMPLE>
0004 putobject                              2
0006 opt_send_without_block                 <calldata!mid:**, argc:1, ARGS_SIMPLE>
0008 opt_send_without_block                 <calldata!mid:-@, argc:0, ARGS_SIMPLE>
0010 leave
=> nil

pp Ripper.sexp '-2 ** 2'
[:program,
 [[:unary, :-@, [:binary, [:@int, "2", [1, 1]], :**, [:@int, "2", [1, 6]]]]]]

pp Ripper.sexp '-2.itself ** 2'
[:program,
 [[:binary,
   [:call,
    [:unary, :-@, [:@int, "2", [1, 1]]],
    [:@period, ".", [1, 2]],
    [:@ident, "itself", [1, 3]]],
   :**,
   [:@int, "2", [1, 13]]]]]

pp Ripper.sexp '-(2.itself) ** 2'
[:program,
 [[:unary,
   :-@,
   [:binary,
    [:paren,
     [[:call,
       [:@int, "2", [1, 2]],
       [:@period, ".", [1, 3]],
       [:@ident, "itself", [1, 4]]]]],
    :**,
    [:@int, "2", [1, 15]]]]]]