+\ ----------------------------------------------------- PROGRAMMING
+
+T{ exists? words }T{ true }T \ high level
+T{ exists? swap }T{ true }T \ in kernel
+T{ exists? lkajsdlakjs }T{ false }T
+
+T{ [defined] if }T{ true }T \ high level
+T{ [defined] dup }T{ true }T \ in kernel
+T{ [defined] k23jh42 }T{ false }T
+
+T{ [undefined] if }T{ false }T \ high level
+T{ [undefined] dup }T{ false }T \ in kernel
+T{ [undefined] k23jh42 }T{ true }T
+