Hmm at least there seems to be a compilation time check for the existance of the package:

lanx@nc10-ubuntu:~$ perl -c -e' my blabla $x;'
No such class blabla at -e line 1, near "my blabla"
-e had compilation errors.
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vs.

lanx@nc10-ubuntu:~$ perl -c -e'{package blabla;} my blabla $x;'
-e syntax OK
[download]