different results in REPL and from a file

[Mateusz]

1. Save the following into the file "example.lisp".
(defun foo () (princ x) (terpri))
(defun bar () (progv '(x) '("progv") (let ((x "let")) (foo))))

(progv '(x) '("progv") (let ((x "let")) (foo)))
(bar)

(defparameter x "defparameter")

(progv '(x) '("progv") (let ((x "let")) (foo)))
(bar)

2. $ sbcl
3. * (load "example.lisp")

Output:
... (some warnings) ...
progv
progv
let
progv
T

$ sbcl --version
SBCL 1.1.18

$ uname -a
Linux mglap 3.16.5-gentoomgkernel #5 SMP Fri Dec 5 18:29:59 CET 2014 x86_64 Intel(R) Pentium(R) CPU 3550M @ 2.30GHz GenuineIntel GNU/Linux

* *FEATURES*
(:ASDF3 :ASDF2 :ASDF :OS-UNIX :NON-BASE-CHARS-EXIST-P :ASDF-UNICODE
 :ALIEN-CALLBACKS :ANSI-CL :ASH-RIGHT-VOPS :C-STACK-IS-CONTROL-STACK
 :COMMON-LISP :COMPARE-AND-SWAP-VOPS :COMPLEX-FLOAT-VOPS :CYCLE-COUNTER :ELF
 :FLOAT-EQL-VOPS :GENCGC :IEEE-FLOATING-POINT :INLINE-CONSTANTS :LARGEFILE
 :LINKAGE-TABLE :LINUX :LITTLE-ENDIAN :MEMORY-BARRIER-VOPS :MULTIPLY-HIGH-VOPS
 :OS-PROVIDES-BLKSIZE-T :OS-PROVIDES-DLADDR :OS-PROVIDES-DLOPEN
 :OS-PROVIDES-GETPROTOBY-R :OS-PROVIDES-POLL :OS-PROVIDES-PUTWC
 :OS-PROVIDES-SUSECONDS-T :PACKAGE-LOCAL-NICKNAMES :RAW-INSTANCE-INIT-VOPS
 :SB-CORE-COMPRESSION :SB-DOC :SB-EVAL :SB-FUTEX :SB-LDB :SB-PACKAGE-LOCKS
 :SB-SIMD-PACK :SB-SOURCE-LOCATIONS :SB-THREAD :SB-UNICODE :SBCL
 :STACK-ALLOCATABLE-CLOSURES :STACK-ALLOCATABLE-FIXED-OBJECTS
 :STACK-ALLOCATABLE-LISTS :STACK-ALLOCATABLE-VECTORS
 :STACK-GROWS-DOWNWARD-NOT-UPWARD :SYMBOL-INFO-VOPS :UNIX
 :UNWIND-TO-FRAME-AND-CALL-VOP :X86-64)

[Douglas Katzman (dougk)]

By putting a 'defparameter' in between two test runs, you've changed the meaning of bindings of X.
The first occurrence of '(let ((x "let"))' is a lexical binding.
The one following defparameter is special because defparameter makes bindings of X pervasively special.
So after loading the above, typing everything in to the REPL again is going to be different as well.