switch with regex

[BCS]

Thoughts please:

pros?

cons?

why it won't work.

-------------
switch(str)
{
case "[Tt]his"~~:
writef("Doing this");
break;

case "[Tt]hat"~~:
writef("Doing this");
break;

case ".*somthing.*"~~:
writef("Doing somthing");
break;

default:
writef("Doing nothing");
break;
}