The best thing is that the whole idea of a "safe string" with a single "quoting" is ... erm ... nonsense.
I mean what makes string "safe" to insert into "INSERT INTO Foo VALUES ('$here') is totally different than what makes it safe to insert into <input ... value="$here"/> or <span onclick="alert('$here')">..., or "open my $IN, $here or die;</c> etc. etc. etc.
It makes sense to mark something "unsafe" (aka. tainted = coming from an non-trusted source), but what makes it safe differs.
OTOH, try to implement something similar (without the use of the builtin tainting!) in Perl. It's also gonna take a bit of code to overload all string operators to work for the String::Safe and String::Unsafe.
Enoch was right!
Enjoy the last years of Rome.