You should probably be specifying destination variables for your options. Otherwise, you will need to predeclare your $opt_x variables with our or use vars. The man page for Getopt::Long is clear on this point:

Default destinations

When no destination is specified for an option, GetOptions will store the resultant value in a global variable named "opt_"XXX, where XXX is the primary name of this option. When a progam executes under "use strict" (recommended), these variables must be pre-declared with our() or "use vars".

It is always a good idea to read the documentation for the modules you choose to use.

-sauoq
"My two cents aren't worth a dime.";