( (square=.!arg^2)
& 1 3 5 7:?numbers
& map$(square.!numbers):?squares2a         { functional form }
& out$!squares2a
& map$((=.!arg^2).!numbers):?squares2b     { functional form with `lambda` }
& out$!squares2b
& :?isquares1
&   whl
  ' ( !numbers:#%?number ?numbers
    & !isquares1 !number^2:?isquares1
    )
& out$!isquares1
);