You seem to have very limited knowledge about your operating system and Perl. I suggest you look at the following:

• If you're on a *nix OS: man ls and man chmod for information about listing and changing file access permissions. If that doesn't mean anything to you, or you're on a different OS, check with a system administrator or read the user manual.
• perlintro -- a brief introduction and overview of Perl
• perlootut - Object-Oriented Programming in Perl Tutorial
• Links on the perl manual page; especially those in the Overview and Tutorials sections.

"3) I do not know how to check the package namespace is correct in both files."

Just look at the code.