EQL function compares object identity, numbers and characters. Numbers are considered as equal only when they have the both same value and type. Result is true if they are same, otherwise false.

(eql 'moo 'moo) => T
(eql 'moo 'foo) => NIL
(eql 1 1) => T
(eql 1 2) => NIL
(eql 1234567890123456789 1234567890123456789) => T

(eql 1.0 1) => NIL
(eql 1.0 1.0) => T

(eql (cons 1 2) (cons 1 2)) => NIL
(let ((x (cons 1 2))) (eql x x)) => T