use Regexp::Exhaustive 'exhaustive';

my @matches = exhaustive(
  'asdf' => qr/..??/,
  qw[ $` $& $' ],
);

printf "%s<%s>%s\n", @$_
  for @matches;

__END__
<a>sdf
<as>df
a<s>df
a<sd>f
as<d>f
as<df>
asd<f>