I read the Symbol Table section of the docs in perlmod before posting, but I don't see how anyone would know after reading that section that my variables are not included in the symbol table.

Using quantifier like anyone is dangerous: no one knows how smart others are. :)

For example, one may be guessing just the opposite: if the variable is "my", then it is not "others'", so it is probably not in package's symbols table for others to modify.