package Foo;

my $dir; # could be 'our' to be visible from outside

# portablitity... far from complete
if ($^O eq 'MSWin32') {
    $dir = 'C:\Users';
} else {
    $dir = '/home';
}

sub import {
    my $package = shift; # just the package name
    if (@_) {
        if (@_ % 2) {
            die "odd number of parameters in ".__PACKAGE__"::import(), aborted";
        }
        my %args = @_;
        if ($args{dir}) {
            $dir = $args{dir};
        }
    }
}
... # more module code
1;