Alright...here's a simple multiplexer:

use strict;
use warnings;

use Getopt::Long;

my ($number, $format) = (2, "output");
GetOptions( 
        "number=i" => \$number,
        "format=s" => \$format,
);

my @output_file;
foreach my $num (1..$number) {
        my $file = "$format.$num";
        open( $output_file[$num-1], ">", $file ) or die "Couldn't open
+ '$file' for write: $!\n";
}

my $file_num = 0;
while(<>) {
        print {$output_file[$file_num]} $_;
        $file_num += 1;
        $file_num %= $number;
}
[download]

Save it in a file of your choosing, and call it like:

perl script.pl --format out --number 7 input1 input2 ...
[download]