Hi @Shadow ,
Along with what @JohnDMoore1 suggested for the substitute, which is a great way to do it, another option can be the following:
Names Default to Here(1);
exurl = {"Test_Yield", "Help_Yield"};
x={};
For(i=1, i<=NItems(exurl), i++,
x[i]=left(exurl[i], Contains(exurl[i], "_Yield")-1);
);
I think one of the things that's throwing the Left command off is that it is a multi-element list -- even though the scripting index says it can deal with lists, it doesn't appear to actually have that ability. The For loop helps to build your output variable as a list. Sometimes this kind of approach is more flexible, especially when you have large data tables and need to rename many columns, etc.
Also, I think there is a mistake in your example url that you gave. You wrote: exurl={"Test_Yield, Help_Yield"}, which is only a single string, not a list. I think what you meant to write is exurl={"Test_Yield", "Help_Yield"} which has the extra quotes and comma separating the elements in the list.
Hope this helps!,
DS