Will our create a package-level variable?

Well, it will create a global variable in the package's namespace. If you want the data to be private to your package, you shouldn't use our; you should put your package in a file by itself (or in a block) and use a lexical variable declared with my instead.

Or should I just be passing around hash-references

Probably, yes. (A single hash ref would probably suffice, right?) For instance, I'd probably have subs something like this:

sub process_search { 
    my $options = shift; 
    # . . .
}
sub simple_search { 
    my $options = { 
        SearchType => simple,    # Contrived parameters for 
        MaxMatches => 10,        # illustrative purposes.
    }; 
    process_search( $options ); 
}
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Any suggestions/advice/criticism encouraged!

I notice you are using prototypes. Don't. At least not until you understand that they aren't anything like what you probably expect coming from a C++ background. Read Tom Christiansen's article about them for a detailed explanation of why they aren't for general use.

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