quiz.rb

QUESTION 6: Write a function multi_gsub that performs multiple, simultaneous
search-and-replace operations on a string.

Example:

"Lorem Ipsum #9191".multi_gsub([[/[a-z]/i, '#'], [/#/, 'P']])
=> "##### ##### P9191"

Answer:
class String
  def multi_gsub(args)
    pairs = args.map {|x| self.scan(x.first).map {|m| [m, x.last] }}  # generate list of substitution pairs
    re = Regexp.union(args.map {|x| x.first})
    self.gsub(re, Hash[*pairs.flatten])
  end
end