use strict;
use warnings;
use Net::FTP;

my $kids;
my @kids = ();
my @fileList = glob("*.pdf");
open(OUT, ">ftp_test.out") or die;

for $kids (1..30){
  my @tempList = @fileList;

  my $start_time = time;
  while(my @files = splice(@tempList, 0, ($#fileList + 1) / $kids)){
    my $pid = fork;
    push(@kids, $pid);
    if($pid == 0){
      #kid
      &FTP_SUB(@files);
      exit;
    }
  }
  waitpid($_, 0) foreach (@kids);
  my $elapsed_time = time - $start_time;
  print OUT "Elapsed time with $kids kids:\t$elapsed_time seconds\n";
  print "Elapsed time with $kids kids:\t$elapsed_time seconds\n";
}


sub FTP_SUB {
  my @files = @_;
  my $start_time = time;
  my $end_time = undef;
  my $host = '...';
  my $user = 'user';
  my $pwd = 'pwd';
  
  my $ftp = Net::FTP->new($host, Debug => 0);

  unless($ftp->login($user,$pass)){
    warn "$$:\tCannot login " . $ftp->message;
  }
  
  unless($ftp->cwd("ftp_test")){
    warn "$$:\tCannot change directory " . $ftp->message;
  }

  foreach my $file (@files){
    unless($ftp->put($file)){
      warn "$$:\tPut failed " . $ftp->message;
    }
  }
  $ftp->quit;
  $ftp = undef;
}
[download]

__OUTPUT__
Elapsed time with 1 kids:    177 seconds
Elapsed time with 2 kids:    92 seconds
Elapsed time with 3 kids:    64 seconds
Elapsed time with 4 kids:    56 seconds
Elapsed time with 5 kids:    40 seconds
Elapsed time with 6 kids:    34 seconds
Elapsed time with 7 kids:    28 seconds
Elapsed time with 8 kids:    27 seconds
Elapsed time with 9 kids:    24 seconds
Elapsed time with 10 kids:    23 seconds
Elapsed time with 11 kids:    22 seconds
Elapsed time with 12 kids:    20 seconds
Elapsed time with 13 kids:    19 seconds
Elapsed time with 14 kids:    18 seconds
Elapsed time with 15 kids:    19 seconds
Elapsed time with 16 kids:    17 seconds
Elapsed time with 17 kids:    15 seconds
Elapsed time with 18 kids:    17 seconds
Elapsed time with 19 kids:    16 seconds
Elapsed time with 20 kids:    16 seconds
Elapsed time with 21 kids:    15 seconds
Elapsed time with 22 kids:    14 seconds
Elapsed time with 23 kids:    13 seconds
Elapsed time with 24 kids:    12 seconds
Elapsed time with 25 kids:    15 seconds
Elapsed time with 26 kids:    13 seconds
Elapsed time with 27 kids:    13 seconds
Elapsed time with 28 kids:    13 seconds
Elapsed time with 29 kids:    13 seconds
Elapsed time with 30 kids:    13 seconds
[download]