use warnings;
use strict;

# this just generates an example input file, not part of the solution
open my $tfh, '>', 'input.txt' or die $!;
print $tfh "$_\n" x (rand(3)+1) for 'A'..'Z';
close $tfh;

# now split the input file
my $MAXSIZE = 20;
open my $ifh, '<', 'input.txt' or die $!;
my $outcount=0;
open my $ofh, '>', 'out000.txt' or die $!;
my $prev;
while (<$ifh>) {
	chomp;
	if (defined $prev && $prev ne $_) {
		print STDERR "Record type switched from $prev to $_, output size is ".tell($ofh)."\n";
		if (tell($ofh)>$MAXSIZE) {
			close $ofh;
			my $ofn = sprintf 'out%03d.txt', ++$outcount;
			print STDERR "Opening new output file $ofn\n";
			open $ofh, '>', $ofn or die $!;
		}
	}
	print $ofh $_, "\n";
	$prev = $_;
}
close $ofh;
close $ifh;