/* PL/I has immediate facilities for all those operations except for */
/* replace. */
s = t;                     /* assignment */
s = t || u;                /* catenation - append one or more bytes. */
if length(s) = 0 then ...  /* test for an empty string.              */
if s = t then ...          /* compare strings.                       */
u = substr(t, i, j);       /* take a substring of t beginning at the */
                           /* i-th character andcontinuing for j     */
                           /* characters.                            */
substr(u, i, j) = t;       /* replace j characters in u, beginning   */
                           /* with the i-th character.               */

/* In string t, replace every occurrence of string u with string v.  */
replace: procedure (t, u, v);
   declare (t, u, v) character (*) varying;

   do until (k = 0);
      k = index(t, u);
      if k > 0 then
         t = substr(t, 1, k-1) || v || substr(t, k+length(u));
   end;
end replace;