use strict;
use warnings;

sub print_header {
	my ( $max, $indent ) = @_;

	$indent = " " x $indent;
        my $maxlen=length $max;

	# Create a header so they can see what column things are on
	my @top;
	foreach my $num ( 1 .. $max ) {
		my $r = 0;
		foreach my $char ( split //, sprintf( "% ${maxlen}s", $num ) ) {
			$top[ $r++ ] .= $char;
		}
	}
	# print the header
	print $indent. join ( "\n" . $indent, @top ), "\n"; 
	# print a divider line
	print $indent. ( "-" x $max ) . "\n";               
}

sub split_lines {
	my ( $max, $x, $y, $z ) = @_;

	# $max is the maximum length of a line
	# $x,$y,$z are the lines to be split and displayed

	print_header( $max, 2 );   # two because of the "> " from below

	while ( length($x) || length($y) || length($z) ) {

		# while any of our strings have content left within
		# cut out the first $max chars and print them
		# with a blank line seperating the groups
		s/^(.{0,$max})//s 
			and print "> $1\n" 
				for $x, $y, $z;
		print "\n";
	}
}

sub generic {
	my $max = shift;

	my @lines  = @_;
	my $indent = length(@lines);

	print_header( $max, $indent + 2 ); # +2 because of the "> " below

	PRINT: {

		# while any of our strings have content left within
		# cut out the first $max chars and print them
		# with a blank line seperating the groups
		$lines[$_] =~ s/^(.{0,$max})//s
			and printf "% ${indent}s> %s\n", $_ + 1, $1 
				for 0 .. $#lines;
		print "\n";
		length($_) and redo PRINT for @lines;
	}
}

my $x = "CATGACTTCTAATCGCACTG";
my $y = " ****  ****** *** *";
my $z = "CCATTCTGACTGACTTTCAG";

print "The pretty task specific version:\n";
split_lines( 15, $x, $y, $z );

print "The generic version:\n";
generic( 15, $x, $y, $z, $x, $y, $z, $x, $y, $z, $x, $y, $z );

__END__
The pretty task specific version:
           111111
  123456789012345
  ---------------
> CATGACTTCTAATCG
>  ****  ****** *
> CCATTCTGACTGACT

> CACTG
> ** *
> TTCAG

The generic version:
             111111
    123456789012345
    ---------------
 1> CATGACTTCTAATCG
 2>  ****  ****** *
 3> CCATTCTGACTGACT
 4> CATGACTTCTAATCG
 5>  ****  ****** *
 6> CCATTCTGACTGACT
 7> CATGACTTCTAATCG
 8>  ****  ****** *
 9> CCATTCTGACTGACT
10> CATGACTTCTAATCG
11>  ****  ****** *
12> CCATTCTGACTGACT

 1> CACTG
 2> ** *
 3> TTCAG
 4> CACTG
 5> ** *
 6> TTCAG
 7> CACTG
 8> ** *
 9> TTCAG
10> CACTG
11> ** *
12> TTCAG