sub parent
{
 while($line = <FILE>)
 {
  if(#line =~ something)
  {
    $parsed =  child(*line,*FILE);
    if($parsed =~ /##_XYZ_##/)
    {
      my @tempArray = split /##_XYZ_##/,$parsed;
      $line = "$tempArray[1]";
      redo;  
    }
    else
    {
      continue...further....   
    } 
  }
 }
}

sub child
{
  my *cLine = shift;
  my *FILE  = shift;
  my $temp = <FILE>;
  if(test($temp ))
  {
   return $cLine."##_XYZ_##"."$temp";
  }
  else
  {
    ...continue further...
  }
 }