Restrict Apache forward proxy to a remote url set

Question

Is there a robust way to restrict Apache forward proxy to a set of remote URLs?

Now I can see the only solution with multiple identical <Proxy "..."> blocks as:

<Proxy "http://example1.com">
...
</Proxy>
<Proxy "http://example2.com">
...
</Proxy>
<Proxy "http://example3.com">
...
</Proxy>

-- that is not suitable.

Thanks for any tips.