Opening file: 'file2.txt'
   beg:   'AAA'   end:   'EOAAA'
   first: 'AAA'

AAA
  text1
  text2
  text3
EOAAA
------------------------------

Opening file: 'file1.txt'
   beg:   'SEGMENT3'   end:   'EOS3'
   first: 'SEGMENT3'

SEGMENT3
  text5
  text6
  text7
  text8
------------------------------

Opening file: 'file3.txt'
   beg:   'P333'   end:   'EOP333'
   first: 'FILE3'

FILE3

P201
  text1
  text2
  text3
EOP201

P333
  text4
EOP333
------------------------------