Firefox and Safari both allow calling regular expression objects as...

src/flag-definitions.h

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 126 matching lines @@
 // compilation-cache.cc
 DEFINE_bool(compilation_cache, true, "enable compilation cache")
 
 // debug.cc
 DEFINE_bool(remote_debugging, false, "enable remote debugging")
 DEFINE_bool(trace_debug_json, false, "trace debugging JSON request/response")
 DEFINE_bool(debugger_auto_break, false,
             "automatically set the debug break flag when debugger commands are "
             "in the queue (experimental)")
 
-// execution.cc
-DEFINE_bool(call_regexp, false, "allow calls to RegExp objects")
-
 // frames.cc
 DEFINE_int(max_stack_trace_source_length, 300,
            "maximum length of function source code printed in a stack trace.")
 
 // heap.cc
 DEFINE_int(new_space_size, 0, "size of (each semispace in) the new generation")
 DEFINE_int(old_space_size, 0, "size of the old generation")
 DEFINE_bool(gc_global, false, "always perform global GCs")
 DEFINE_int(gc_interval, -1, "garbage collect after <n> allocations")
 DEFINE_bool(trace_gc, false,
@@ skipping 222 matching lines @@
 #undef FLAG
 
 #undef DEFINE_bool
 #undef DEFINE_int
 #undef DEFINE_string
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META