use strict;
use warnings;

sub process_para {
   my ($para) = @_;
   if (my ($id) = $para =~ /^(\w+)/) {
      if ($id ne 'blabla5') {
         $para =~ s/^TEXT TO BE REMOVED\n//mg;
      }
   }
   print($para);
}

{
   my ($depth, $buf);
   while (<DATA>) { 
      $buf .= $_;
      ++$depth if /\(\s*$/;
      --$depth if /^\s*\)\s*$/;
      #printf("[%d] %s", $depth, $_);
      if (!$depth) {
         process_para($buf);
         $buf = '';
      }
   }

   die("Bad nesting\n") if $depth;
}

__DATA__