String handling function, substring vs. substr

[arsi@xxxxxxxxxxxxxx]

Hi all,

I want to call one of the two functions above many times (in an aggregate 
function) and it says in the manual pages that substr is the same as 
substring.

Does this mean that substr calls substring internally?? Or is it the other 
way around?? Or are they independent of each other??

So in short, which is faster to use??

Thanks,

Archie