sub make_handle {
        ...
    }

    our $handle = make_handle(); # "... used only once"

##</code><code>##

sub foo {
    my $foo = shift;
    return undef unless defined $foo;
    no warnings 'redefine';
    *foo = sub { $foo };
    foo();
}

{
    my $bar;
    sub bar {
        defined $bar ? $bar : ($bar = shift);
    }
}