DB<9> use constant FAILED => ();
 
  DB<10> use constant FALSE => !1;
 
  DB<11> use constant TRUE => 1;
 
  DB<12> sub t_FALSE  { return FALSE; }
 
  DB<13> sub t_TRUE  { return TRUE; }
 
  DB<14> sub t_FAILED  { return FAILED; }
 
  DB<15> if (@a=t_FAILED) {print "TRUE"} else {print "FALSE" }
FALSE
  DB<16> if (@a=t_FALSE) {print "TRUE"} else {print "FALSE" }
TRUE
  DB<17> if ($a=t_FALSE) {print "TRUE"} else {print "FALSE" }
FALSE
  DB<18> if ($a=t_FAILED) {print "TRUE"} else {print "FALSE" }
FALSE