why exactly does it evaluate to `~$* ?
In short, the `~$* text that $* evaluates to, acts as a marker to allow for search-and-replace of this marker (with $1, $2, etc) after the evaluation of the line is fully complete. What the marker looks like is not important, as long as it can't reasonably be the result of the evaluation of anything other than $*. `~$* is "weird" enough to fulfill that requirement.
