gsub replacement via hash

gsub-hash.rb

replace = {'{{HAPPY}}' => 'sad', '{{FUN}}' => 'lame', '{{BALLS}}' => 'rock'}
subject = "{{HAPPY}} {{FUN}} {{BALLS}} are amazing"

search = Regexp.new(replace.keys.map{|k,v| "(#{k})"}.join('|'))
parsed = subject.gsub(search, replace)

puts "old: #{subject}"
# => old: {{HAPPY}} {{FUN}} {{BALLS}} are amazing

puts "new: #{parsed}"
# => new: sad lame rock are amazing