The following example generates such an error due to the end of the range in the second PERFORM statement:
$set ilshowperformoverlap ... perform a thru c. perform c thru b. goback. *> Errors are displayed as follows: a section. *> COBCH1663E Overlapping perform range: 2 entries display "In a". *> COBCH1664E perform range: a thru c b section. display "In b". c section. *> COBCH1664E Perform range: c thru b display "In c". *> COBCH1667E perform range end before start go to a.