ways of mutating wordlist content

[CoD3 Br3aK3r]

i currently have a rather large wpa wordlist containing totally random passkeys eg "A5dscF342b" and so on
i was wondering if there is a tool or method available to mutate those passkeys in various ways ?
such as splitting them in half and swapping the halfs around eg (1234567890) to (0987612345)
or swapping every other character eg (1234567890) to (1324657980)

i am familiar with programs such as "mangle" and the likes but either im not using them right or it simply doesn't cater for my needs
if anyone knows a way to do this i would be very interested in learning how
many thanks

[blackMORE]

crunch comes to mind!

[CoD3 Br3aK3r]

i can use crunch to generate random keys no problem..
do you know the rules to specify to make it work with an existing list tho..