rb_hash_keys     4299 hash.c             rb_define_method(rb_cHash,"keys", rb_hash_keys, 0);
rb_hash_keys      347 struct.c           ary = rb_hash_keys(list);
rb_hash_keys      512 struct.c           rest = rb_hash_keys(rest);
rb_hash_keys     2059 vm_eval.c          VALUE ary = rb_hash_keys(vars->tbl);