while (<FILE>) {
    next unless /\S/; # Skip whitespace lines
    if (/^ \s* Daniel \s+ Lastname \s* $/x) {
        $current_handle = daniels_handle;
        next;
    }
    elsif (/^ \s* Steffi \s+ Lastname \s* $/x) {
        $current_handle = steffis_handle;
        next;
    }

    print $current_handle $_;
}