In helm-swoop minibuffer, insert text saved in registers

Question

This is my usecase:

1. Open file1
2. store the text in register a using C-x r s a
3. Go to another place, store the text in register a using C-x r s b
4. Go to file, store the text in register a using C-x r s c
5. Invoke helm-swoop
6. Insert the content of the registers a, b, c with \| i.e. (text_in_rega\|text_in_regb\|text_in_regc\)
7. M-i
8. This will show me the grep like across files, I can use C-c C-e and edit multiple files at once and save them.
9. This is a big time saver in verilog.

Answer 1

;; STrip text properties - taken from https://stackoverflow.com/questions/8372722/print-only-text-discarding-text-properties

(defun strip-text-properties(txt)
  (set-text-properties 0 (length txt) nil txt)
      txt)

;;new function        
(defun swoop-test0 ()
    (interactive)
   (let ((ctext (concat "\\(\\_<" (strip-text-properties (get-register ?a)) "\\_>\\|\\_<"  (strip-text-properties (get-register ?b)) "\\_>\\)")))
    (helm-swoop :$query ctext )
   )
  )

I need to make it more clean by checking if the register is nil.