That doesn't match his example very well. I would think it was a fine solution except he said his example works. His example seems to return (or print really) a list consisting of every possible reversal of a single pair of neighboring letters. I.e. transposition_list('foobar') would be the list ('ofobar', 'foobar', 'foboar', 'foobra'). I'm not sure how to handle double letters like the 'oo' in 'foo' but his doesn't handle them specially.

I don't know if I really would do it this way but here is my untested first crack at it:

print "$_\n" for transposition_list('thisisatest'); 

sub transposition_list {
    my $string = shift; 
    my @transpositions; 

    for my $i (0 .. length($string)-2) { 
        (my $tmp = $string) =~ s/(.{$i})(.)(.)/$1$3$2/;
        push @transpositions, $tmp; 
    }

    return @transpositions; 
}
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-sauoq
"My two cents aren't worth a dime.";