Syntax:

gosub <label>
label:
  [statements]
  return

The GOSUB command calls a subroutine marked by a label. Return will pass control back to the caller. Nesting subroutines are supported (`GOSUB` and `RETURN` compiles to just plain `JSR` and `RTS`, nothing fancy). Stack overflow is not checked in runtime, but is quite unlikely to encounter. Example:

rem ** subroutines **
gosub first_routine
end

first_routine:
	print "hello world"
	gosub second_routine
	return
	
second_routine:
	print "and hello again"
	return

Note #1: make sure to use the `END` command before your routines if you don't want them to be executed in the normal program flow (like in the example above).

Note #2: there is no runtime call stack checking (e. g. no `?RETURN WITHOUT GOSUB ERROR`). If your call stack is corrupted, the program is likely to break.

Note #3: Unlike procedures, subroutines do not open a new local scope.