Regular Expressions 101

Explanation
Pro

Definition Group(?(DEFINE) (?<taboo> \h* (?<!\pL) (?:we|you) (?!\pL) \h*) )

Group taboo(?<taboo> \h* (?<!\pL) (?:we|you) (?!\pL) \h*)

\h*any horizontal whitespace character, repeated any number of times

Negative Lookbehind(?<!\pL)

\pLany Unicode letter

Non-Capturing Group(?:we|you)

1st Alternativewe

wethe literal text we (case insensitive)

2nd Alternativeyou

youthe literal text you (case insensitive)

Negative Lookahead(?!\pL)

\pLany Unicode letter

\h*any horizontal whitespace character, repeated any number of times

Non-Capturing Group(?: (?&taboo) )*

*repeats the group contents below any number of times:

(?&taboo)calls group taboo as a subroutine

Group 2( (?: (?! (?&taboo) ) \N)* )

Non-Capturing Group(?: (?! (?&taboo) ) \N)*

*repeats the group contents below any number of times:

Negative Lookahead(?! (?&taboo) )

(?&taboo)calls group taboo as a subroutine

\Nany non-newline character

Non-Capturing Group(?: (?&taboo) )*

*repeats the group contents below any number of times:

(?&taboo)calls group taboo as a subroutine

\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match

Global pattern flags

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

g modifier: global. Finds all matches instead of stopping after the first

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25 tokens

(?(DEFINE) (?<taboo> \h* (?<!\pL) (?:we|you) (?!\pL) \h*) )  (?: (?&taboo) )* ( (?: (?! (?&taboo) ) \N)* ) (?: (?&taboo) )* \K

There are no unit tests.