"""Calculate a fast similarity score between two strings based on common prefix and suffix.

The score is inversely proportional to the similarity of the strings, meaning a lower score indicates
more similar strings. The score is computed by summing the lengths of both strings and subtracting
twice the combined length of the common prefix and suffix.

Args:
    s1 (str): The first string to compare.
    s2 (str): The second string to compare.

Returns:
    float: A similarity score where a lower value indicates more similar strings. The score is
           calculated as `len(s1) + len(s2) - 2.0 * (prefix_len + suffix_len)`, where `prefix_len`
           is the length of the common prefix and `suffix_len` is the length of the common suffix.

Note:
    - If the strings are identical, the score will be 0.0.
    - If the strings share a common prefix or suffix, the score will be reduced accordingly.
    - If the strings have no common prefix or suffix, the score will be the sum of their lengths.
"""