I think libapl contains the full APL interpreter, to interface with a GUI, not any separate exports of its functionality, function-wise.
Can you give me an example of a functionality from APL that you can not express in Pascal? FreePascal supports many good vector libraries.
Btw: I know that notation-wise APL can be very dense, a Pascal equivalent is probably less dense, but possibly much faster since it is compiled to native code.
Recent improvements in array handling and low-level vector support in modern Pascal dialects would probably bridge the gap a bit.