Free Form CHAIN with RRN

/free
 rrn = 3425;

 chain rrn FILE1;
 if (not %found(FILE1));
   // do something
 endif;

 *inlr = *on;
 return;
/end-free

The paranthesis around the key on the CHAIN opcode must be omitted if you want to access the file by the relative record number.