Only two experimental features were removed:

• Passing a reference to key/values/each

  I don't know why that was released in the first place given it was known to be broken before it was even coded.

• my $_;

  It was causing code like apply { s/foo/bar/ } @a to break in a manner that was confusing for too many.

Smart-matching and given/when have been experimental for a while, but they are not dead. The subject came up again this week. There are strong intentions to fix it.