Am I missing some important fact about interning symbols in LISP?

Question

To be brief. Here is my several tries to intern and use a symbol in clisp.

 [1]> (setq sym (intern \"foo\"))
 |foo|
 [2]> (eq sym \'foo)
 NIL

Answer 1

The case-sensitivity of the Common Lisp reader is determined by the readtable:

(readtable-case *readtable*)

Typically the reader will initially intern symbols in uppercase (unless you explicitly escape characters). Hence:

(eq (intern "foo") 'foo) => NIL

(eq (intern "FOO") 'foo) => T

(eq (intern "FOo") 'fo\o) => T

You can use backquote syntax to build the form for eval:

(let ((abc 2))
  (eval `(+ 2 ,abc)))

=> 4