Non-Capturing Group(?:(?:"?((\w+)\b.*\b)"?)\s)? ?repeats the group contents below at most once:
Non-Capturing Group(?:"?((\w+)\b.*\b)"?) "?optionally matches the literal " (3410 / 428 / 2216)
\w+any word character, repeated at least once
\ban ASCII word boundary
.*any character (except for line terminators), repeated any number of times
\ban ASCII word boundary
"?optionally matches the literal " (3410 / 428 / 2216)
\sany whitespace character
<?optionally matches the literal < (6010 / 748 / 3C16)
Group 3(([\w@]*)@(\w*)\.[a-zA-Z]{2,3}) *matches any number of characters from the set below:
\wany word character
@the literal @ (6410 / 1008 / 4016)
@the literal @ (6410 / 1008 / 4016)
\w*any word character, repeated any number of times
\.the literal . (4610 / 568 / 2E16)
Character Class[a-zA-Z]{2,3} {2,3}matches between 2 and 3 characters from the set below:
a-zone character from a (9710) to z (12210) (case insensitive)
A-Zone character from A (6510) to Z (9010) (case insensitive)
>?optionally matches the literal > (6210 / 768 / 3E16)
,?optionally matches the literal , (4410 / 548 / 2C16)
g modifier: global. Finds all matches instead of stopping after the first
i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters