my $in_paragraph;
my $bar;
my %ignore;
while (<FH>) {
   if (m/start of paragraph/) {
       $in_paragraph = 1;
       $bar = 0
       next;
   }
   if (m/end of paragraph/) {
       $in_paragraph = 0;
       next;
   }
   if (m/line with bar/) {
       $bar = 1;
       next;
   }
   if (m/line with ref (\d+)/) {
       if ($begin and $bar and not $end) {
           $ignore{$1} = 1;
       }
       next;
   }
}