`.freeze` on regex literal seems to just add extra VM instruction to freeze the string.

```
irb(main):059:0> puts RubyVM::InstructionSequence.compile('/\A\s*\z/').disasm
== disasm: <RubyVM::InstructionSequence:<compiled>@<compiled>>==========
0000 trace            1                                               (   1)
0002 putobject        /\A\s*\z/
0004 leave
=> nil
irb(main):060:0> puts RubyVM::InstructionSequence.compile('/\A\s*\z/.freeze').disasm
== disasm: <RubyVM::InstructionSequence:<compiled>@<compiled>>==========
0000 trace            1                                               (   1)
0002 putobject        /\A\s*\z/
0004 opt_send_simple  <callinfo!mid:freeze, argc:0, ARGS_SKIP>
0006 leave
```