Old news? Randomise strings but not first and last letter?

Aocdrnicg to a rsecareh at Cmbagrdie Uinervtisy, it denos't mtater waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be at the rghit pclae.The rset can be a total mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
This might not be complete truth, by I gave it a try. So can you. You will need Tie::DictFile for this to work (installable from CPAN using cpan shell for example), but other than that you are set.

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use strict;
use Tie::DictFile;

# based on
# http://www.perlmonks.org/index.pl?node_id=227240

sub shuffleStr {
my $len = length $_[0];
my ($tmp, $n);
$n = $_+rand($len-$_)
, $tmp = substr( $_[0], $_, 1)
, substr( $_[0], $_, 1) = substr( $_[0], $n , 1)
, substr( $_[0], $n , 1) = $tmp
for 0 .. $len;

my %dict;
tie %dict, 'Tie::DictFile';

sub rnd4 {
my ($f,$m,$l) = @_;
my $word = $f.$m.$l;
if (exists $dict{$word}) {
return $f.shuffleStr($m).$l;
} else {
return $word;

while() {