Yes, GNU APL is quite slow. There was some primitive implemented in GNU APL (as part of the interpreter, in c). A pure-APL implementation running on dyalog ou

Yes, GNU APL is quite slow. There was some primitive implemented in GNU APL (as part of the interpreter, in c). A pure-APL implementation running on dyalog outperformed it by a considerable margin. If you're looking for a performance, opensource APL, try j. Though if performance is not a priority then, as the sibling says, dzaima/apl or april should be more than adequate.