#!/usr/bin/perl
use strict;
use warnings;

use Data::Dumper;

my $text   = 'Vorrede bla bla Anfang <<A>> Teil1 <<A>> Teil2 <<B>> Teil3 <<A>> Ende Nachrede.';
my $retext = 'Anfang <<A>> [^<]+ (<<A>>) [^<]+ (<<B>>) [^<]+ <<A>> Ende';
print "Original:\n",
      "text    : [$text]\n",
      "retext  : [$retext]\n";

my $magicnumber = 0;
while ($text =~ s~(?<=\D)>>~#$magicnumber>>~) {
    ++$magicnumber;
}
$retext =~ s~>>~#\\d+>>~g;
my $re  = qr~$retext~;
print "\nVeraendert:\n",
      "text    : [$text]\n",
      "retext  : [$retext]\n",
      "re      : [$re]\n";

my @allmatch = $text =~ $re;
my ($m1, $m2, $m3) = ($`, $&, $');

print "\nallmatch: ", Dumper \@allmatch;
print "m1      : [$m1]\n",
      "m2      : [$m2]\n",
      "m2      : [$m3]\n";