A bit nasty, since I'm fiddling with the pos, but it does the trick without modifying the original string and temp variables: 

my $str = "thisisatest";
while ($str =~ /(.)(.)/g) {
    print "$`$2$1$'\n";
    pos($str)--;
}

[download]

Just my 2 cents, -gjb-

In reply to Re: Transposition of each letter pair in string by gjb
in thread Transposition of each letter pair in string by Cody Pendant

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