#!/usr/bin/perl
#
# simple fasta input file cleaver
# usage: cleaver.pl --format OUTPUT_FILE_PREFIX --number X input_file
# where X is the number of files to split input_file into
#
# note: you can optionally pass more than one input file 
#       to (re)combine into X files

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;
}

my $file_num = 0;
while(<>) {
	$/='>';
	chomp;
	my $pre = ($. != 2 ? ">" : ""); 
	print {$output_file[$file_num]} "$pre$_";
	next if $. == 1;
	$file_num +=1;
	$file_num %= $number;
}