(Untested) Example XP service class, created at start of each map.

BonsaiXPService.cs

// Toxic Frog:
// To utilize, simply copy/paste the BonsaiXPRecord class into the main files of Bonsai XP. Then copy the
// code within the event and merge it with the main event handler you already have established. The fewer
// the handlers, the better performance is.
Class BonsaiXPRecord
{
	Class<Actor> mo;
	int XP;
}

Class BonsaiXPEvent : EventHandler
{
	// A Map<k,v> could be used here but it would force the requirements to be
	// GZDoom 4.10+ only.
	private Array<BonsaiXPRecord> Records;
	private Array<Class<Actor> > Classes; // For faster indexing.
	
	// Call this when WorldThingDied occurs.
	private void GiveXP(Actor mo, Actor to)
	{
		if (!mo || !to)	return;
		
		// Do your thing here.
	}
	
	// Handles setting up of customizable XP settings. Right now this only handles
	// the classes directly. More work will need to be done if parent checking
	// is to be done.
	override void WorldLoaded(WorldEvent e)
	{
		SetupXPRecords();
	}
	
	private void SetupXPService()
	{
		Records.Clear();
		Classes.Clear();
		
		// Find all services with the name 'BonsaiXPService' in it, and 
		// iterate through each one.
		let it = ServiceIterator.Find("BonsaiXPService");
		Service XPServ;
		while (XPServ = it.Next())
		{
			int i = 0; // Reset for each service class.
			String ret = "";
			Array<String> st; 
			while (true)
			{
				ret = XPServ.GetString("GetXP", "", i++);
				
				// Nothing else to process. Next service class!
				if (ret.Length() < 1)
					break;
					
				// Remove spaces and tabs
				st.Clear();
				ret.Replace("	", "");
				ret.Replace(" ", "");
				
				// Split based on token characters.
				ret.Split(st, ",");
				
				// Invalid format, so skip it.
				if (st.Size() < 1)
				{
					Console.Printf("%s: Invalid format. Comma needed between actor name & XP");
					continue;
				}
				
				// Check if it's a valid actor class.
				Class<Actor> cls = st[0];
				if (!cls)
					continue;
					
				// Now construct the record.
				BonsaiXPRecord rec;
				
				// Find it first if it already exists.
				int ind = Classes.Find(cls);
				if (ind < Classes.Size())
					rec = Records[ind];
				else
				{
					rec = new('BonsaiXPRecord');	
					rec.mo = cls;
				}
				rec.XP = st[1].ToInt();
				Classes.Push(cls.GetClassName());
			}
		}
	}
	
}
// If it has the name 'BonsaiXPService' and it inherits from Service, the iterator
// will find it.
Class PlaceHolder_BonsaiXPService : Service
{	
	// You could just rely on the GetInt variant if the plan is to keep it simple.
	// However this way strikes me as more user friendly, and this is all only
	// called once, upon entering a new map. Syntax is as follows:
	// <Actor Name>, <XP Amount>
	static const String mon[] =
	{
		"TM_Skeleton,				1",
		"TM_Zombie,				1",		
		"TM_Spider,				1"
	};	
	
	// Do not modify anything below here.
	private clearscope String ProcessCmdStr(String req, String str, int i, double d, Object o) const
	{
		if (req ~== "GetXP")
		{
			if (i >= 0 && i < mon.Size())
				return mon[i];
		}
		return "";
	}
	
	override String GetString(String request, String stringArg, int intArg, double doubleArg, Object objectArg)
	{	return ProcessCmdStr(request, stringArg, intArg, doubleArg, objectArg);	}
	
	override String GetStringUI(String request, String stringArg, int intArg, double doubleArg, Object objectArg)
	{	return ProcessCmdStr(request, stringArg, intArg, doubleArg, objectArg);	}
}