The errors mean that strict is working. Stick with the lower-case version as this is the correct one. When you say "use strict" you should expect errors as this is forcing you to write good code.

The fact that "use Strict;" does not give you errors is interesting. It suggests that you have a package somewhere named Strict.pm. One more bit of knowledge is that the standard for package names is for them to start with upper-case so that they don't interfere with perl's pragmas like strict.