The `exit()` function terminates the running program with the given exit
code or 0 in case no argument is given or if the argument cannot be
converted to an integer.

The function does not return.

-- Testcase --
{%
	print("Before invoking exit()\n");

	exit();

	print("After invoking exit()\n");
%}
-- End --

-- Expect stdout --
Before invoking exit()
-- End --

-- Expect exitcode --
0
-- End --


Passing a code argument overrides the default "0" value.

-- Testcase --
{%
	exit(123)
%}
-- End --

-- Expect exitcode --
123
-- End --