New code:
immutable nfields = header.count('\t');
...
output.writeln(cycle("\t-").take(2 * nfields));
output.writeln("\t-".repeat(nfields).join);
New code:
immutable nfields = header.count('\t');
...
output.writeln(cycle("\t-").take(2 * nfields));
output.writeln("\t-".repeat(nfields).join);