package Foo;
    use OI qw(oi);
    use strict;
    our ($pkg_var1, $pkg_var2);

    $pkg_var1 = 'var 1';
    $pkg_var1 = 'var 2';
    
    my $sub = oi(in  => 'example.html')
    $sub->('page title', 'header line');