How to negate a regular expressin, which is stored in a varible:

$_ = "a b";

/[^$save]/o and die "Unsafe";

# perl v 5.6.1 on debian woody returns
# Unmatched ) before HERE mark in regex

I know that fore this keys I have other possibilities how to write it.
But this is a demonstration what I consider as bug.
Why perl searches for ending / inside the compiled subexpression?

$_ = "a b";
/$save/ and die "Unsafe";