# =~ 返回匹配位置（nil 表示不匹配）
"Hello" =~ /ll/   # 2
"Hello" =~ /xx/   # nil

# match —— 返回 MatchData
m = "Hello World".match(/Wo(..)d/)
m[0]   # "World"（完整匹配）
m[1]   # "rl"（第一个捕获组）

# match? —— 返回布尔（Ruby 2.4+）
"Hello".match?(/ll/)  # true

# sub —— 替换第一个
"Hello World".sub(/o/, "0")    # "Hell0 World"

# gsub —— 替换所有
"Hello World".gsub(/o/, "0")   # "Hell0 W0rld"

# 块形式
"Hello".gsub(/\w+/) { |m| m.upcase }  # "HELLO"

"a1b2c3".scan(/\d/)       # ["1", "2", "3"]
"a1b2c3".scan(/(\w)(\d)/) # [["a","1"], ["b","2"], ["c","3"]]

# 捕获组
m = "2024-07-23".match(/(\d{4})-(\d{2})-(\d{2})/)
m[1]  # "2024"
m[2]  # "07"
m[3]  # "23"

# 命名组
m = "2024-07-23".match(/(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/)
m[:year]   # "2024"
m[:month]  # "07"