1true;  ``; echo $?
2false; ``; echo $?
3true;  `""`; echo $?
4false; `""`; echo $?
5true;  `     `; echo $?
6false; `     `; echo $?
7
8true;  $(); echo $?
9false; $(); echo $?
10true;  $(""); echo $?
11false; $(""); echo $?
12true;  $(     ); echo $?
13false; $(     ); echo $?
14
15exec ''; echo $?
16echo Not reached
17