(let* ((epoch (or (tointz (getenv "SOURCE_DATE_EPOCH")) 0))
       (isotime (time-string-utc epoch "%FT%T+00:00"))
       (pdf (file-get-string "txr-manpage.pdf"))
       (start (search-str pdf "<?xpacket begin="))
       (end (if start (search-str pdf "<?xpacket end" start)))
       (xml (if end [pdf start..end]))
       (orig-len (len xml)))
  (unless xml
    (format *stderr* "XML block not found in PDF")
    (exit nil))
  (upd xml
    (regsub #/uuid:........-....-....-....-............/
            "uuid:00000000-0000-0000-0000-000000000000")
    (regsub #/Date>....-..-..T..:..:..-..:../
            `Date>@isotime`))
  (assert (eql (len xml) orig-len))
  (set [pdf start..end] xml)
  (file-put-string "txr-manpage.pdf.temp" pdf)
  (rename-path "txr-manpage.pdf.temp" "txr-manpage.pdf"))