#! /usr/bin/perl

use strict;
use warnings;

my $file = 'test.dat';
my $out  = 'test.dat.out';
my $count_ = 1;
my $datensatz = '';

{
  open(my $outfh,">$out") or die $!;

  open(my $fh,"<$file") or die $!;
  while(my $entry = <$fh>){
    $entry =~ s/\r?\n//g;
    if($entry =~ /^\s*?#/){
      print $outfh $entry,"\n";
    }
    else{
      if($entry =~ /^\s*?$/){
        $count_++;
      }
      else{
        $datensatz .= $entry."\n";
      }
      if($count_ % 3 == 0){
        $datensatz = getDatensatz($datensatz);
        print $outfh $datensatz;
        $count_ = 1;
        $datensatz = '';
      }
    }
  }
  if($datensatz){
    $datensatz = getDatensatz($datensatz);
    print $outfh $datensatz;
  }
  close $fh;
  close $outfh;
}

sub getDatensatz{
  my ($entry) = @_;
  my $bool = 0;
  my $set = '';
  my @steigend;
  for my $line(split(/\r?\n/,$entry)){
    chomp $line;
    my $wert = (split(/\s+/,$line))[-1];
    $bool = 1 if($bool || $wert =~ /^4/);
    unless($bool){
      push(@steigend,$line);
    }
    else{
      $set .= $line."\n";
    }
  }
  $set .= $_."\n" for(@steigend);
  $set .= "\n\n";
  return $set;
}