If your strings are always going to be formatted in the same way,it's easy:

#!/usr/bin/perl

use strict;
use warnings;

while(<DATA>) {

      chomp;
     (my $text, my $numerical) = split(/\./,$_,2);

      print "$text: \n";
      print "$numerical: \n";
}
__DATA__
abc.1.0.1.0
bnnn.1.0.1.1
dnnnnn.1.0.2.0
[download]

Note that this assumes there is a period separating the text part from the numerical part (it looks like a version number to me ;-) ). I also almost always chomp input, mostly because I want to have explicit control over when \n's get inserted and not rely on end-of-record markers in input data.