foreach my $val (@values){
        $val *= $df * 50 ;
    }
    print join("\t", @values), "\n";

##</code><code>##

    print join("\t", map { $_ * $df * 50 } @values), "\n";

##</code><code>##

...
while (<FILE>){
    print join("\t", map { $_ * $df * 50 } split /\t/), "\n";
}