Regular Expressions 101

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`
^(?:([\w]*)(?: (.*))? )?([\w]+)$
`
gm
^ asserts position at start of a line
Non-capturing group
(?:([\w]*)(?: (.*))? )?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
1st Capturing Group
([\w]*)
Match a single character present in the list below
[\w]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\w matches any word character (equivalent to [a-zA-Z0-9_])
Non-capturing group
(?: (.*))?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
2nd Capturing Group
(.*)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
3rd Capturing Group
([\w]+)
Match a single character present in the list below
[\w]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\w matches any word character (equivalent to [a-zA-Z0-9_])
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.

Regular Expression
No Match

`
`
gm

Test String

Substitution

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Code Generator

Generated Code

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Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression