(define (combine-syms lst)
  (let loop ((l lst) (res '()))
    (cond ((null? l) (string-intersperse (reverse res)))
          ((not (list? (car l)))
           (loop (cdr l) (cons (->string (car l)) res)))
          ((every (lambda (e) (not (number? e))) (car l))
           (loop (cdr l) (append (map ->string (car l)) res)))
          (else (cons (string-intersperse (reverse res)) l)))))