0]  # cat test_range
while( $text=<DATA> ){
  print "$. $text";
  if ( ($text=~/^AAAAAA/) .. ($text=~/^BBBBBB/ ) ){
     if ($text=~/^AAAAA/){
        print "========= Start of the fragment detected at $.\n";
     }
     print "Still true at $.\n";
     $end=$.; # Is this the only way to detect the end of the fragment?
  }
}
print "========= End of the fragment detected at $end.\n";
__DATA__
aaa
aaa
AAAAAA
ccc
ddd
BBBBBB
111
222
333
CCCCCC
444
555
666
DDDDDD
777
888
999

##</code><code>##

[0]  # perl  test_range
1 aaa
2 aaa
3 AAAAAA
========= Start of the fragment detected at 3
Still true at 3
4 ccc
Still true at 4
5 ddd
Still true at 5
6 BBBBBB
Still true at 6
7 111
8 222
9 333
10 CCCCCC
11 444
12 555
13 666
14 DDDDDD
15 777
16 888
17 999
========= End of the fragment detected at 6.