Use of uninitialized value in length at ./jumble.pl line 34, <DATA> line 1.
Use of uninitialized value in split at ./jumble.pl line 34, <DATA> line 1.
Use of uninitialized value in concatenation (.) or string at ./jumble.pl line 36, <DATA> line 1.
Use of uninitialized value in split at ./jumble.pl line 33, <DATA> line 1.

##</code><code>##

use strict;
use warnings;
use List::Util 'shuffle';

while (<DATA>) {
    my @newline = split(/\b/);
    for my $word (@newline) {
        my $first = "";
        my $rem = "";
        my $middle = "";
        my $last = "";
        ($first, $rem)  = split /(?<=\b\w)/, $word;
        ($middle, $last) = split /(?=(\w'\w+|\w)$)/, $rem;
        ((length $middle) == 2) ? $middle = reverse $middle :
        ($middle = join "", shuffle(split //, $middle));
         print "$first$middle$last";
    }
}

##</code><code>##

__END__
I couldn't believe that I was actually understanding what I was reading.
The phenomenal power of the human mind, according to research at Cambridge University,
suggests that it doesn't matter in what order the letters in a word are, as long as
the first and last letters are in the right place. The rest can be a total mess,
and you can still read it without a problem. This is because the human mind does
not read every letter by itself, but the word as a whole. Amazing, huh? Yeah,
and I always thought spelling was important!
Check apostrope and punctuation: Jame's, They're, we'll they'd.