Would have been nice to see you code so we could show you where you are going wrong. But this seems to do what you want.

#!/usr/bin/perl

use strict;
use warnings;

my $data = do { local $/; <DATA> };

my @data = $data =~ /STARTP(.*?)ENDP/sg;

foreach (@data) {
  my @titles = /TITLE(.*?)ENDTITLE/sg;
  $_ = \@titles;
}

foreach my $i (0 .. $#data) {
  print "Block $i\n";
  foreach my $j (0 .. $#{$data[$i]}) {
    print "Title $j:\n$data[$i][$j]\n";
  }
  print "\n";
}

__DATA__
STARTP
TITLE
some gibberish
some more gibberish
ENDTITLE
TITLE
some gibberish
some more gibberish
ENDTITLE
TITLE
some gibberish
some more gibberish
ENDTITLE
ENDP
STARTP
TITLE
some gibberish
some more gibberish
ENDTITLE
TITLE
some gibberish
some more gibberish
ENDTITLE
TITLE
some gibberish
some more gibberish
ENDTITLE
ENDP
[download]