Since you have written only two pairs of (capturing) parentheses, you only get two match variables. A quantified capture stores only the string of the last match.

So either make the outer parenthesis capture, and use split to extract the numbers from $1, or write out four pairs of capturing parenthesis.

Note that this is more convenient in Perl 6: a quantified capture records a list of all matches.

Thanks for the quick answer guys.

Unfortunately four groups is not going to help, it should match anthing from 1.2 to 1.2.3.4.5.6 etc, or anything follows this structure.

To look for a substring matching  [\d+\.]+ is also not an option, as there may be other matches in the string, like a simple number.

CPAN search of "ip" ... Net::IP::Match::Regexp

Sorry, I don't understand your answer. What exactly is wrong with the approach that uses split?

$_ = '1.2.3.4.5.6 foo bar';
if (/((?:\d+\.)+(\d+)/) {
    my @matches = (split(/\./, $1), $2)
}
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Perl 6 - second systems done right

I'm thinking you don't need a beefy regex if that's all you want to do. How about something like this instead:

my $string = '12.34.56.78 asdfasdfasdfasdfasdf';

my $numbers = shift @{[split ' ', $string]};
my @numbers = split '\.', $numbers;

use Data::Dumper;
print Dumper(@numbers) if $numbers =~ /^[\d.]+$/;
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EDIT: Whoops, sorry moritz - I confess to only skimming your answer and didn't notice that you had already suggested using split. Apologies!

(?i-msx:(?:(\d+)\.)+(\d+))

matches as follows:
  
NODE                     EXPLANATION
----------------------------------------------------------------------
(?i-msx:                 group, but do not capture (case-insensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (?:                      group, but do not capture (1 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    (                        group and capture to \1:
----------------------------------------------------------------------
      \d+                      digits (0-9) (1 or more times
                               (matching the most amount possible))
----------------------------------------------------------------------
    )                        end of \1
----------------------------------------------------------------------
    \.                       '.'
----------------------------------------------------------------------
  )+                       end of grouping
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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Here is one way to get what you want:

use warnings;
use strict;

$_ = "1.2.17.3 Glückwunschschreiben 12 und";
if ( /(\d+)\.(\d+)\.(\d+)\.(\d+)/ ) {
    print "$1   $2   $3  $4\n";
}

__END__

1   2   17  3
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$_ = "1.2.17.3 Glückwunschschreiben 12 und";
say for /\G([0-9]+)[. ]/g;
__END__
1
2
17
3
[download]

good stuff, it works!