use warnings;
use strict;

while (<DATA>)
    {
    chomp;
    my @sentences = split /(?<=\.)\s*/;
    
    #print '>', join ("<\n>", @sentences), '<';
    foreach(@sentences){
		print "$_\n";
	}
    }

__DATA__
Hello world. Hello Bretheren. Goodbye spaces. All I really want are se
+ntences.
[download]
Which prints:

Hello world.
 Hello Bretheren.
 Goodbye spaces.
 All I really want are sentences.


Your code

>Hello world.<
>Hello Bretheren.<
>Goodbye spaces.<
>All I really want are sentences.<

I would like:
 
Hello world.
Hello Bretheren.
Goodbye spaces.
All I really want are sentences.