Your solution is probably looking for a way to methodically parse out the headings and data for each section, rather than look for only a specific one. For that, you would want to use a zero width look ahead assertion (?=regexp). One assumption, the headings aren't always (but usually) indented with 5 spaces. Line items are always indented with 9 spaces. Here's what I came up with that worked for me on ActivePerl 5.6.

use strict;

my $data = join("", <DATA>);
print "data:\n$data";
# loop for each heading
while ($data =~ /\s*(.*?):\s*\n((.|\n)*?\n)(?=(\s*\w+:|\Z))/gc) {
   print "heading: $1\n";
   my $text = $2;
   while ($text =~ /\s{9}(.*?)\n/gc) {
      print "line item: $1\n";
   }
   
}

exit;

__DATA__
     Paragraph1: 
         text
     Paragraph2: 
         text1
         text2
         text3
     Paragraph3:
         text
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