X:\>subst
E:\: => C:\windows
F:\: => C:\

X:\>perl readdir.pl
A: No such file or directory
B: Invalid argument
C:
D:
E: . ..
F:
G: No such file or directory
H: . ..
I: . ..
J: No such file or directory
K: No such file or directory
L: No such file or directory
M: . ..
N: No such file or directory
O: No such file or directory
P: No such file or directory
Q: No such file or directory
R: . ..
S: No such file or directory
T: . ..
U:
V: . ..
W: No such file or directory
X:
Y: No such file or directory
Z: Invalid argument

X:\>