for my $file (@list_of_files) {

    open my $read, '<', $file or die $!;
    my $count = 0;
    my $new_name = "$file$count";
    open my $write, '>', $new_name or die $!;
    while (my $line = <$read>) {
        print $write $line;
        if ($. % 25 == 0 and not eof $read) {
            $count++;
            close $write;
            $new_name = "$file$count";
            open $write, '>', $new_name or die $!;
        }
    }
}

#!/usr/bin/perl

use strict;
use warnings;

my $dateiname='liste%s.txt';
my $lines_per_file=25;


my @files=@ARGV;
die "Bitte Dateien angeben\n" unless(@files);

my $file_cnt=1;
my $out="";
my $line_cnt=0;
for my $file (@files)
{
 if(open(my $fh,'<',$file))
 {
  while(my $line=<$fh>)
  {
   $line_cnt++;
   chomp($line);
   $out.="$line\n";
   if($line_cnt>=$lines_per_file)
   {
    my $file_out_name=;
    write_out($out,sprintf($dateiname,$file_cnt));
    $file_cnt++;
    $out="";
    $line_cnt=0;
   }
  }
 }
 else
 {warn "Konnte $file nicht oeffnen ($!)\n"}
}
write_out($out,sprintf($dateiname,$file_cnt)) if($out ne '');

####################################
sub write_out
{
 my ($data,$file)=@_;
 open(my $fhout,'>',$file) or die "Konnte $file nicht oeffnen ($!)\n";
 print $fhout $data;
 close($fhout);
}