use strict;
use warnings;
use Benchmark;

my $line = 'x' x 18_000;

open my $frontend, '>>', '/dev/null' or die $!; 

Benchmark::cmpthese(-1, {
   _regex   => \&_regex,
   _unpack1 => \&_unpack1,
   _unpack2 => \&_unpack2
});

sub _regex {
    my $tmp_line = $line;
    if( length $tmp_line < 4000 ){
        $tmp_line .= "\t" x 5;
    }   
    else{
        $tmp_line =~ s/(.{4000})/$1\t/g;
    }   
    print $frontend $tmp_line;
}

sub _unpack1 {
    my $tmp_line = $line;
    my $laenge = length($tmp_line); 
    if($laenge <=4000) {
        print $frontend "$tmp_line\t\t\t\t\n";
    }   
    elsif($laenge <= 8000) {
        my ($a, $b) = unpack("A4000 A4000", $tmp_line);
        print $frontend "$a\t$b\t\t\t\n";
    }   
    elsif($laenge <= 12000) {
        my ($a, $b, $c) = unpack("A4000 A4000 A4000", $tmp_line);
        print $frontend "$a\t$b\t$c\t\t\n";
    }   
    elsif($laenge <= 16000) {
        my ($a, $b, $c, $d) = unpack("A4000 A4000 A4000 A4000", $tmp_line);
        print $frontend "$a\t$b\t$c\t$d\t\n";
    }   
}

sub _unpack2 {
    my $tmp_line = $line;
    my $len = length($tmp_line);
    my $pos = 0;
    my $tab = 5;
    while ( my $s = unpack("x$pos A4000", $tmp_line) ) { 
        $tab--;
        print $frontend "$s\t";
        $pos += 4000;
        last if $pos >= $len;
    }
    print $frontend "\t" x $tab;
    print $frontend "\n";
}

             Rate   _regex _unpack2 _unpack1
_regex    19814/s       --     -39%     -93%
_unpack2  32582/s      64%       --     -88%
_unpack1 265564/s    1240%     715%       --