Hi @kshg7030,
Is this for a website, or for a mobile app?
For both, yes you could use Processing Rules, and yes, you have limited control to set up if logic (there is no true "else" logic, but you can order the rules and add conditions to catch various scenarios).
If this is for a mobile app, this is likely your only option; assuming of course that you don't just tell your developers what values to send under what conditions and test it to make sure it works as expected.
And in case you say "but mobile apps don't have URLs....", ALL our mobile apps set the equivalent URL in the tracking.
Now, if you are talking about web, I wouldn't use processing rules... I would use Adobe Launch, and use a custom code Data Element to write out the logic of what you want (actually, this isn't even a "I would" situation, this is exactly what I do... though less based on the URL, and more based on a series of factors like what is the page type, and other data layer values that I have at my disposal)
Essentially, I create a custom code Data Element like so:

Then in the code editor, I will code the logic:
var url = _satellite.getVar('url'); // assuming you have a data element for the url]
var pagename = "unknown";
if (url.indexOf('/?xyz') > -1){
pagename = "a";
}
else if (url.indexOf('/abc') > -1){
pagename = "b";
}
....
return pagename;
The _statellite.getVar statement gets the value of "url" Data Element... while yes you could reference this through all your code (in all the if statements), it's less efficient to keep retrieving the value then to just set a variable that you can use in your logic (and if you need the test or change something, it's easier to change one line than everywhere in your code).
I like the set an initial pagename of "unknown" so that I can monitor if something is slipping past the logic that isn't setting a proper name... you don't have to do that, you could just set it to an initial value of ""
The return statement sets the final value to the Data Element, then I can use the data element as any other DE in my implementation.