class String
def mgsub(key_value_pairs=[].freeze)
regexp_fragments = key_value_pairs.collect { |k,v| k }
gsub(Regexp.union(*regexp_fragments)) do |match|
key_value_pairs.detect{|k,v| k =~ match}[1]
end
end
end
"GO HOME!".mgsub([[/.*GO/i, 'Home'], [/home/i, 'is where the heart is']])
# => "Home is where the heart is!"
"Here is number #123".mgsub([[/[a-z]/i, '#'], [/#/, 'P']])
# => "#### ## ###### P123"
"between".mgsub([[/ee/, 'AA'], [/e/, 'E']]) # Good code
# => "bEtwAAn"