ltsv2tsv.rb

data = []
columns = []

ARGF.each_line do |line|
  data << Hash[line.split("\t").map do |kv|
    k, v = kv.split(':', 2)
    columns << k unless columns.include?(k)

    [k, v]
  end]
end

puts columns.join("\t")
data.each do |datum|
  puts(columns.map do |column|
    datum[column]
  end.join("\t"))
end