while (<FILE>) {
    next unless /\S/; # Skip whitespace lines
    if (/^ \s* Daniel \s+ Lastname \s* $/x) {
        $printto = "Daniel";
    }
    elsif (/^ \s* Steffi \s+ Lastname \s* $/x) {
        $printto = "Steffi";
    }
    elsif ($printto eq "Daniel") {
         print DANIEL $_;
    }
    elsif ($printto eq "Steffi") {
         print STEFFI $_;
    }
}