tab_counter.rb

tab_count = 0
File.readlines('/path/to/file').each do |line|
  # The regexp looks for 1 or more tabs at the beginning of the line as a group.
  # We then split the result by character, then get the size of the Array from the split.
  # Only do all that if the line matches the regexp in the first place.
  tab_count += line.match(/^([\t]+)/)[1].split('').size if line.match /^([\t]+)/
end