my $result = printf ...
...
my $data = printf ...

##</code><code>##

my $result = sprintf("%8.3f", $col3); # column 3 format

# loop over remaining columns
for my $c (@columns) {
    my $data = sprintf("%10.3f", $c);
    $result .= " $data";  # append $result
}

print $output "$result\n";