An implementation of interpreted string literals, inspired by Python's
Literal String Interpolation <https://www.python.org/dev/peps/pep-0498/>
and Docstrings <https://www.python.org/dev/peps/pep-0257/> and Julia's
Triple-Quoted String Literals
<https://docs.julialang.org/en/v1.3/manual/strings/#Triple-Quoted-String-Literals-1>.