$success = TRUE;
if substr("test", 2) != "st" $success = FALSE;
if defined substr("test", 5) $success = FALSE;

if substr("test", 1, 3) != "es" $success = FALSE;
if not defined substr("test", 4, 4) $success = FALSE;
if substr("test", 4, 4) != "" $success = FALSE;
if defined substr("test", 5, 5) $success = FALSE;
if substr("test", 0, 5) != "test" $success = FALSE;
if defined substr("test", 4, 3) $success = FALSE;
