Not a perfect shuffle, but close (enough?) and much shorter: 

perl -M5';$x=join"",sort{rand()<rand}a..z'
     -pe 'eval"tr/0-9/$x/"' input.txt

[download]
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice. Suck that fhit

In reply to Re: A little golfing challenge: replace digits by random letters by BrowserUk
in thread A little golfing challenge: replace digits by random letters by haukex

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