perldoc -f crypt:
Traditionally the result is a string of 13 bytes:
two first bytes of the salt, followed by 11 bytes
from the set "[./0-9A-Za-z]", and only the first
eight bytes of the encrypted string mattered, but
alternative hashing schemes (like MD5), higher
level security schemes (like C2), and implementa-
tions on non-UNIX platforms may produce different
strings.

When choosing a new salt create a random two char-
acter string whose characters come from the set
"[./0-9A-Za-z]" (like "join '', ('.', '/', 0..9,
'A'..'Z', 'a'..'z' )[rand 64, rand 64]").\n\n

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