If you indented your code a bit, it would be a lot easier to read :-)

Looks like you're making it all a bit more complex than it needs to be. Here's a program that I wrote to do the same thing - perhaps it will be useful to you.

#!/usr/bin/perl

use strict;
use warnings;

use POSIX 'ceil';

die "Usage: splitfile num_of_files initial_file\n" unless @ARGV >= 2;

my ($count, $infile) = @ARGV;

open INFILE, '<', $infile or die $!;

my @lines = <INFILE>;

my $lines_per_file = ceil(@lines / $count);

my $i = 1;

open OUTFILE, '>', "$infile.$i" or die $!;

my $lines_left = $lines_per_file;

foreach (@lines) {
  unless ($lines_left) {
    close OUTFILE;
    $i++;
    open OUTFILE, '>', "$infile.$i" or die $!;
    $lines_left = $lines_per_file;
  }

  print OUTFILE;
  $lines_left--;
}
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