Since this is so much fun, let's do one that uses both the regex and the substr :)

my $word = 'jigglewort';
print $word, "\n";

while ($word =~ /(.)(.)/g) {
  my $tmp = $word;
  substr($tmp, pos($word)-2, 2) = "$2$1";
  print $tmp, "\n";

  pos($word) = pos($word) - 1;
}

=for output
jigglewort
ijgglewort
jgiglewort
jigglewort
jiglgewort
jiggelwort
jigglweort
jiggleowrt
jigglewrot
jigglewotr
=cut
[download]