use strict;
use warnings;

open (FH, "<message_log01") or die "Could not open source file. $!";

my $i = 0;

while (1) {
    my $chunk;
	print "process part $i\n";
	open(OUT, ">part$i.log") or die "Could not open destination file";
	$i ++;
	if (!eof(FH)) {
		read(FH, $chunk, 1000000);
		print OUT $chunk;
	} 
	if (!eof(FH)) {
		$chunk = <FH>;
		print OUT $chunk;
	}
	close(OUT);
	last if eof(FH);
}