1. How to tell if a module is installed: perldoc Module or perl -MModule -ce 1
2. How to install a module from CPAN: use the CPAN module (perl -MCPAN -e shell) or follow the instructions that come with the downloaded module.
3. How to write to a filehandle opened for writing: the IO::File node here on PerlMonks appears to be corrupted. Use perldoc to read the documentation on your local system; it does include examples of writing to an IO::File object.

Regarding your code question... Globs cannot be declared with my. However, if you change the first line to: *bighandle = openafile(); then everything in the same package can access bighandle directly. (And code in other packages can access it as, for example, main::bighandle.)