I asked my pal Barry Shein, who many of you know, if he had his PL/1 syntax horror lying around, and he did.  He said: "this was tested on the Iron Spring Software PL/1 compiler running on openSuSe Linux (http://www.iron-spring.com/)"

IBM still uses PL/1.  Remember, the main definition of "legacy" is "revenue-producing."

TRY:PROC OPTIONS(MAIN);
   DCL (IF,THEN,ELSE) FIXED BINARY (31);

   IF = 1;
   THEN = 2;
   ELSE = 3;

   IF IF = THEN THEN THEN = IF ; ELSE ELSE = THEN;

END TRY;