Language fallback chain or mapping for languages with variants (e.g. Chinese)

I will use Chinese as an example:

Basic mappings:

• zh -> zh-Hans
• zh(?:-Hans)?-(?:CN|SG|MY) -> zh-Hans
• zh(?:-Hant)?-(?:TW|HK|MO) -> zh-Hant

In case some phrases are regional and you want to implement a more complete fallback chain:

• zh-MY -> zh-SG -> zh-CN -> zh-Hans (basically zh-CN)
• zh-MO -> zh-HK -> zh-TW -> zh-Hant (basically zh-TW)

Reference: