Nice debugging tip! Readers should note that not all SAS programming environments support an interactive mode, in which you can submit one statement at a time and see immediate results in a single SAS procedure. Display Manager (a.k.a. "PC SAS") does support it, of course, as well as the dedicated SAS/IML Studio. SAS Studio supports interactive mode if you toggle the toolbar button "Go interactive" -- then your debugging example can work. SAS University Edition (based on SAS Studio) supports this. SAS Enterprise Guide does not support an interactive mode -- but it does have that excellent DATA step debugger for...well...DATA steps.