The issue is that if the parentheses only appear once in the regular expression and you use a repetition to represent your match like (\d){8}, you will repeatedly overwrite the same buffer. Probably the clearest solution is using the repetition operator x in constructing the string for your regular expression:

#!/usr/bin/perl
use strict;
use warnings;

$_ = 'somename   1000  0.24  280  2 2576.9  2731.9  12.0  4195.3';
my $regex =   '(^[a-z]\w*)'
            . '\s+([\.\d]+)' x 8
            . '$';

my (@array) = /$regex/io;
print join "\n", @array;
__END__
somename
1000
0.24
280
2
2576.9
2731.9
12.0
4195.3
[download]

Note as well that if you are operating on the special variable $_ there is no need to bind it to the regular expression.

You can also construct that in the regular expression itself using A bit of magic: executing Perl code in a regular expression, as described in perlretut.