Heres a quick script I knocked up:

use strict;
use warnings 'all';

unless(open(FH,'<test.dat'))
{
    die "Could not open file\n";
}
my $temp;

while(sysread(FH,$temp,5,0))
{
    print $temp,"\n";    
}

close(FH);
[download]

and the data file (save as test.dat)

1234567890abcdefghijklmnopqrstuvwxyz
[download]

It prints

12345
67890
abcde
fghij
klmno
pqrst
uvwxy
z
[download]

HTH