use YAPE::Regex::Explain;
print YAPE::Regex::Explain->new(
qr/AAA\w+?AAA/
)->explain;
__END__
The regular expression:

(?-imsx:AAA\w+?AAA)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  AAA                      'AAA'
----------------------------------------------------------------------
  \w+?                     word characters (a-z, A-Z, 0-9, _) (1 or
                           more times (matching the least amount
                           possible))
----------------------------------------------------------------------
  AAA                      'AAA'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------