execute$() -- execute a user defined subroutine, which must return a string
execute$ can be used to execute a user defined subroutine, whose name may be specified as a string expression.
This feature is the only way to execute a subroutine, whose name is not known by the time you write your program. This might happen, if you want to execute a subroutine, which is compiled (using the compile command) during the course of execution of your program.
Note however, that the execute$-function is not the preferred method to execute a user defined subroutine; almost all cases you should just execute a subroutine by writing down its name within your yab program (see the example).
return a$+" "+b$
The example simply prints Hello world!, which is the return value of the user defined subroutine foo$. The same could be achieved by executing: