+repeats the group contents below at least once:
Group 2(PK\s(?!.*PK\s+\w))? ?repeats the group contents below at most once:
PKthe literal text PK (case sensitive) \sany whitespace character
Negative Lookahead(?!.*PK\s+\w) .*any character (except for line terminators), repeated any number of times
PKthe literal text PK (case sensitive) \s+any whitespace character, repeated at least once
\wany word character
\s*any whitespace character, repeated any number of times
\w+any word character, repeated at least once
\s*any whitespace character, repeated any number of times
,the literal , (4410 / 548 / 2C16)