#!/usr/bin/perl

use strict;
use warnings;

my $file = 'ausgabedatei_des_tools.txt';

{
  open my $fh, '<', $file or die $!;
  local $/,"\n\n";
  while( my $entry = <$fh> ){
    my ($htb) = $entry =~ /(htb\s*\d+\.\d+)/;
    print $htb,"\n";
  }
}