use Regexp::Exhaustive qw(exhaustive);
use Data::Dumper;

my $str = "A dun A dun B overlapped B something A again B";
print Dumper [ exhaustive($str => qr/A (.*?) B/) ];


__END__
$VAR1 = [
  "dun A dun",
  "dun A dun B overlapped",
  "dun A dun B overlapped B something A again",
  "dun",
  "dun B overlapped",
  "dun B overlapped B something A again",
  "again"
];