I have no problems with the anonymous sub. I do take issue, though, with the list of scalars for options. I much prefer to use a hash to keep things in one place.

But hang on! If you mispell a scalar, the compiler will bark at you. If you mispell a hash key, the runtime will autovivify it for you. Hmm.

But that's ok too, because what I really prefer doing is hiding it all away in a scope, and declaring subs as The Only Way of retrieving values. Admittedly, you still don't get a compile time error, but it will blow up at runtime if you get things worng. My template looks something like:

{
    use Getopt::Long;
    my %opt;
    GetOptions (
        \%opt,
        qw/ verbose! file:s debug+ help/
    ) || die sub { print <<END_OF_HELP;
$0: you blew it! Switches are as follows:
    --help | -h  this help screen
...
END_OF_HELP
    }
    sub debug   { exists $opt{debug} ? $opt{debug} : 0 }
    sub verbose { exists $opt{verbose} ? 1 : 0 }
    sub file    {
        if( not exists $opt{f} ) {
            ''
        }
        elsif( not defined $opt{f} ) {
            '/etc/passwd'
        }
        else {
            $opt{f}
        }
    }
}
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The sub file lets you distinguish between an argument that is absent (return an empty string), present, but with no value (return a fixed name) or present with a value (return the value).

Since the %opt hash isn't available outside the scope, the program can't (accidentally or on purpose) modify the contents. This may be construed as a feature.