process_gsub.rb

def Process.gsub pat, sub
  mem  = File.open('/proc/self/mem', 'r+')
  maps = File.open('/proc/self/maps')

  maps.each do |map|
    from, to, perms, offset = map.scan(/(\h+)-(\h+) (\S+) (\h+)/)[0]

    if perms['rw']
      from, to = [from, to].map { |addr| addr.hex + offset.hex }
      data = mem.tap { |m| m.seek from }.read(to - from) rescue next

      i = -1
      while i = data.index(pat, i + 1)
        match = data[pat]
        mem.seek(from + i)
        mem << data[i, match.size].sub(pat, sub)
      end
    end

    break if map[/\[heap\]$/]
  end

  mem.close
  maps.close
end

def foo
  puts 'This is strange.'
  puts 'This is foolish.'
end

foo
Process.gsub(/(This is) [a-z]+\./, '\1 amazing!')
foo