\$the literal $ (3610 / 448 / 2416)
\Kresets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
\s*any whitespace character, repeated any number of times
Group 1((?:[^<$\s]+|(?!\s+[<$])\s+)*) Non-Capturing Group(?:[^<$\s]+|(?!\s+[<$])\s+)* *repeats the group contents below any number of times:
Negated Character Class[^<$\s]+ +matches at least one character outside the set below:
<the literal < (6010 / 748 / 3C16)
$the literal $ (3610 / 448 / 2416)
\sany whitespace character
2nd Alternative(?!\s+[<$])\s+ Negative Lookahead(?!\s+[<$]) \s+any whitespace character, repeated at least once
<the literal < (6010 / 748 / 3C16)
$the literal $ (3610 / 448 / 2416)
\s+any whitespace character, repeated at least once
\s*any whitespace character, repeated any number of times
Positive Lookahead(?=(?:<(*ACCEPT)|\$|$)(*SKIP)(*F)) Non-Capturing Group(?:<(*ACCEPT)|\$|$) 1st Alternative<(*ACCEPT) <the literal < (6010 / 748 / 3C16)
(*ACCEPT)immediately succeeds the current match or subroutine; inside an assertion, resolves it according to whether it is positive or negative
\$the literal $ (3610 / 448 / 2416)
$end of string, or before its final line terminator
(*SKIP)acts like (*PRUNE), but the next unanchored match attempt starts where (*SKIP) was reached instead of at the next subject character
(*F)forces the current match attempt to fail at this position