Create a file and execute it from a .wdl script

In the past I wrote some code which created string which contained a short program,
Forgotten how I executed this string(code)
'execute' seems to do as I require but having trouble defining the string.
UPDATE!!!
t
THE BELOW SEEMS TO WORK
Sorry to have wasted your time!
string mission_str1 = "beep();";

function t_test()
{
//beep();
execute(mission_str1); // executes the string
}
ON_T = t_test;