use strict;

# first slurp the file
my $content = do {
                    local $/;
                    open my $fh, "<", "in.txt" or die $!;
                    <$fh>
                 };

# then split it into chunks
my @chunks = $content =~ /##Flag##(.*?)##CloseFlag##/sg;

# now analyze the chunks
for my $chunk (@chunks) {
   my ($first, $last) = $chunk =~ /T:(\d+).*?(\d+)\D*$/s;

   # count number of newlines
   my $newlines = $chunk =~ tr/\n/\n/;

   print "first-last: ", $first - $last, "# of lines: ", $newlines-1, "\n";
}