description: Hello world with function definition and call
text:
- def: hello
  function:
    name: str
    lastName: {optional: str} # optional parameter
  return:
    if: ${ lastName is defined }
    then: Hello ${ name } ${ lastName }!
    else: Hello ${ name }!
- call: ${ hello }
  args:
    name: World
    lastName: Universe
