erm, rtfm :)

From Crypt::CBC:

 $cipher = Crypt::CBC->new( -key    => 'my secret key',
                             -cipher => 'Blowfish',
                             -salt   => 1
                           );
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and...

 -salt           Enables OpenSSL-compatibility. If equal to a value
                    of "1" then causes a random salt to be generated
                    and used to derive the encryption key and IV. Othe
+r
                    true values are taken to be the literal salt.
[download]

and...

The -salt argument actives an OpenSSL-compatible method of generating 
+the encryption/decryption key and IV. If salt has the value "1", then
+ a random salt is computed (highly recommended). Any other non-false 
+value will be interpreted as the bytes of the actual salt to use. If 
+you provide the salt, it must be exactly 8 bytes in length. It is hig
+hly recommended that you use -salt=>1, as this may become the default
+ in future versions of this module.
[download]

I think that pretty much says it all :)