or download this
C:\test>perl -M-warnings=uninitialized,numeric,once,void -E"123;$x=1;p
+rint $y; 'A'+0"
...
Name "main::x" used only once: possible typo at -e line 1.
Use of uninitialized value $y in print at -e line 1.
Argument "A" isn't numeric in addition (+) at -e line 1.