provide a namespace that was not package-level to prevent accidental use of "global" variables

For clarification:

Variables declared with my are not package variables. At file-level, they are file scoped, so will be accessible from the declaration until the end of file. When declared inside a block, they are only accessible until the end of that block.

Package variables are declared with our or use vars and are accessible from inside the package they are declared in.

Also, package variables can be accessed by their fully qualified names from anywhere. So, in that sense, are also "global".