Check substring in string

subs.rb

def subs(str1, str2)
  return nil if str2.size > str1.size

  str1.each_char.with_index do |char, index|
    next if char != str2[0]

    match = true
    str2[1..].each_char.with_index do |_, str2_slice_index|
      str2_index = str2_slice_index + 1
      next if str2[str2_index] == str1[index + str2_index]

      match = false
      break
    end

    return index if match
  end

  nil
end