Globals in ruby which really are native C functions pretending to be globals.

ruby_pseudo_globals.c

// Ruby 2.3.1
/* eval.c:1614:    */ rb_define_virtual_variable("$@", errat_getter, errat_setter);
/* eval.c:1615:    */ rb_define_virtual_variable("$!", errinfo_getter, 0);
/* io.c:12280:     */ rb_define_virtual_variable("$_", rb_lastline_get, rb_lastline_set);
/* load.c:1195:    */ rb_define_virtual_variable("$\"", get_loaded_features, 0);
/* load.c:1196:    */ rb_define_virtual_variable("$LOADED_FEATURES", get_loaded_features, 0);
/* process.c:7537: */ rb_define_virtual_variable("$?", rb_last_status_get, 0);
/* process.c:7538: */ rb_define_virtual_variable("$$", get_pid, 0);
/* re.c:3653:      */ rb_define_virtual_variable("$~", match_getter, match_setter);
/* re.c:3654:      */ rb_define_virtual_variable("$&", last_match_getter, 0);
/* re.c:3655:      */ rb_define_virtual_variable("$`", prematch_getter, 0);
/* re.c:3656:      */ rb_define_virtual_variable("$'", postmatch_getter, 0);
/* re.c:3657:      */ rb_define_virtual_variable("$+", last_paren_match_getter, 0);
/* re.c:3659:      */ rb_define_virtual_variable("$=", ignorecase_getter, ignorecase_setter);
/* re.c:3660:      */ rb_define_virtual_variable("$KCODE", kcode_getter, kcode_setter);
/* re.c:3661:      */ rb_define_virtual_variable("$-K", kcode_getter, kcode_setter);
/* safe.c:127:     */ rb_define_virtual_variable("$SAFE", safe_getter, safe_setter);
/* time.c:5092:    */ rb_define_virtual_variable("$find_time_numguess", find_time_numguess_getter, NULL); // #ifdef DEBUG_FIND_TIME_NUMGUESS