\Dmatches any character that's not a digit (equivalent to [^09])
1st Capturing Group
((00\+)?55(\s\.)*)?
?matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group
(00\+)?
?matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
1st Alternative
00
00
matches the characters 00 literally (case sensitive)
2nd Alternative
\+
\+matches the character + with index 43_{10} (2B_{16} or 53_{8}) literally (case sensitive)
55
matches the characters 55 literally (case sensitive)
3rd Capturing Group
(\s\.)*
*matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a noncapturing group instead if you're not interested in the data
1st Alternative
\s
\smatches any whitespace character (equivalent to [\r\n\t\f\v ])
2nd Alternative
\.
\.matches the character . with index 46_{10} (2E_{16} or 56_{8}) literally (case sensitive)
3rd Alternative

matches the character  with index 45_{10} (2D_{16} or 55_{8}) literally (case sensitive)
4th Capturing Group
((\()?0?\d{2}(?(5)\))(\s\.)*)?
?matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
5th Capturing Group
(\()?
?matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\(matches the character ( with index 40_{10} (28_{16} or 50_{8}) literally (case sensitive)
0
matches the character 0 with index 48_{10} (30_{16} or 60_{8}) literally (case sensitive)
\d
matches a digit (equivalent to [09])
{2}matches the previous token exactly 2 times
Conditional
(?(5)\))
Conditionally matches one of two options depending on whether the 5th capturing group matched
If condition is met, match the following regex
\)
\)matches the character ) with index 41_{10} (29_{16} or 51_{8}) literally (case sensitive)
Else match the following regex— null, matches any position
6th Capturing Group
(\s\.)*
*matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a noncapturing group instead if you're not interested in the data
1st Alternative
\s
\smatches any whitespace character (equivalent to [\r\n\t\f\v ])
2nd Alternative
\.
\.matches the character . with index 46_{10} (2E_{16} or 56_{8}) literally (case sensitive)
3rd Alternative

matches the character  with index 45_{10} (2D_{16} or 55_{8}) literally (case sensitive)
7th Capturing Group
(9(\s\.)*)?
?matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
9matches the character 9 with index 57_{10} (39_{16} or 71_{8}) literally (case sensitive)
8th Capturing Group
(\s\.)*
*matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a noncapturing group instead if you're not interested in the data
1st Alternative
\s
\smatches any whitespace character (equivalent to [\r\n\t\f\v ])
2nd Alternative
\.
\.matches the character . with index 46_{10} (2E_{16} or 56_{8}) literally (case sensitive)
3rd Alternative

matches the character  with index 45_{10} (2D_{16} or 55_{8}) literally (case sensitive)
\d
matches a digit (equivalent to [09])
{4}matches the previous token exactly 4 times
9th Capturing Group
(\s\.)*
*matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a noncapturing group instead if you're not interested in the data
1st Alternative
\s
\smatches any whitespace character (equivalent to [\r\n\t\f\v ])
2nd Alternative
\.
\.matches the character . with index 46_{10} (2E_{16} or 56_{8}) literally (case sensitive)
3rd Alternative

matches the character  with index 45_{10} (2D_{16} or 55_{8}) literally (case sensitive)
\d
matches a digit (equivalent to [09])
{4}matches the previous token exactly 4 times
Positive Lookahead
(?=\D$)
Assert that the Regex below matches
1st Alternative
\D
\Dmatches any character that's not a digit (equivalent to [^09])
2nd Alternative
$
$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.