根据文档，${1:+ }表示“插入空格 iff 组1被捕获”：

${
  TM_SELECTED_TEXT
  /
    (?<=([A-Za-z])?)      # Lookbehind for and capture ($1) a preceding letter, if any,
    (?:                   # then match a "word" – either
      ([A-Z]+)(?![a-z])   # ($2) 1+ uppercase not followed by a lowercase
    |                     # or
      ([A-Z][a-z]+)       # ($3) an uppercase followed by 1+ lowercase.
    )                     #
  /                       # Replace each match with
    ${1:+\u0020}          # a space, iff group 1 is captured,
    ${2:/upcase}          # the uppercase version of group 2
    ${3:/downcase}        # and the lowercase version of group 3.
  /g                      # for all matches found.
}

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由于$2和$3是互斥的，因此同时使用它们总是会导致实际上只插入一个。
| 之后| After |
| --| ------------ |
| pascal case个| pascal case |
| my UID test个| my UID test |
| fo O ba R个| fo O ba R |
一个更精确（和详细）的版本是（注意，当以JSON字符串编写时，\b需要再次转义："\\b"）：

${
  TM_SELECTED_TEXT
  /
    (?<=                                    # Lookbehind for
      \b                                    # a word boundary followed by
      ([A-Z]+(?![a-z])|[A-Z][a-z]+)*        # 0+ "words"
                                            # and capture the last word, if any.
    )
    (?:([A-Z]+)(?![a-z])|([A-Z][a-z]+))
  /
    ${1:+\u0020}${2:/upcase}${3:/downcase}
  /g
}

型
我在这里使用的是TM_SELECTED_TEXT，但您可能希望根据需要更改它。

我认为要删除行尾的空格，您可以简单地在替换模式的末尾添加一个换行符，并且当您使用带有占位符“MyUIDTest”的片段时，它应该正确地生成“我的UID测试”，而没有任何额外的空格。

${1/(?:([A-Z]+)(?=[A-Z][a-z]))?([A-Z][a-z]+)/$1 ?${2:/downcase} :''/g}\n

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此外，要仅在组1匹配时才在组1后添加空格，可以在替换模式中使用条件语句

${1/(?:([A-Z]+)(?=[A-Z][a-z]))?([A-Z][a-z]+)/$1 ?${2:/downcase} :''/g}

型

感谢@bobblebubble：

${
  TM_SELECTED_TEXT
  /                     # Match either
    (\w)?               # an optional group containing a word character 
    ([A-Z])             # then a group containing an uppercase
    (?=[a-z])           # which is followed by a lowercase
    |                   # or
    ([a-z])(?=[A-Z])    # vice versa.
  /                     #
    $1${1:+ }           # If group 1 was captured, put it back followed by a space.
    $3${3:+ }           # Do the same with group 3.
    ${2:/downcase}      # Finally, insert a lowercased version of group 2.
  /g
}

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