__DATA__
name1   4.5
name3
name5   6.5
name4   -7.9
name6   3.2

##</code><code>##

my @order = qw(name1 name2 name3 name4 name5 name6);
map{/(\S+)\s+(-?[\d.]+)/;$a{$1}=$2?$2:'';print "$1 -- $2 \n";}<DATA>;
map{push(@result,defined $a{$_} ? $a{$_} : 999)}@order;

print join("\n", @result),"\n";

__DATA__
name1   4.5
name3
name5   6.5
name4   -7.9
name6   3.2