1 23 456 789 0123 456
2 24 456 789 0123 456
3 23 456 789 0123 456
4 23 456 789 0123 456
5 23 456 789 0123 456

##</code><code>##


while (<$fd>) {
    my $regex = '^(?:(\d+)\s+)+(\d+)$';

    (my ($d1, $d2, $d3, $d4, $d5, $d6) = $_) =~ m/$regex/;

    print "Line $.\n";
    print "\t$d1\n";

}