# warning win32 doublequotes oneliner                 
perl -e " print $1 if $ARGV[0]=~/(AAA)[^AX].+XXX/"    ABBBAAACCCXXX
AAA

##</code><code>##

perl -MYAPE::Regex::Explain -e " print YAPE::Regex::Explain->new(qr/(AAA)[^AX].+XXX/)->explain(); "
The regular expression:

(?-imsx:(AAA)[^AX].+XXX)

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):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    AAA                      'AAA'
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  [^AX]                    any character except: 'A', 'X'
----------------------------------------------------------------------
  .+                       any character except \n (1 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
  XXX                      'XXX'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------