Hi monks, I have learned OOperl These day, and now had a small question. Below is a sentence chapter 10 package of Programming Perl Third Edition:

You can refer to identifiers5 in other packages by prefixing ("qualifying") the identifier with the package name and a double colon: $Package::Variable.

So,I have tried this:

#!/usr/bin/perl
use warnings;
use strict;
use File::Find;
print $File::Find::Version,"\n";

__OUTPUT__
Name "File::Find::Version" used only once: possible typo at test.pl li
+ne 5.
Use of uninitialized value in print at test.pl line 5.
[download]

What does the error messages mean? And how do I use package variable?
Thanks in advance!