Regular Expressions 101

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/
^(\[(\d+|(?:\d*\.\d+))(?:,\s*(\d+|(?:\d*\.\d+)))*\])\s*[\*x]\s*(\[(\d+|(?:\d*\.\d+))(?:,\s*(\d+|(?:\d*\.\d+)))*\])$
/
gm
^ asserts position at start of a line
1st Capturing Group
(\[(\d+|(?:\d*\.\d+))(?:,\s*(\d+|(?:\d*\.\d+)))*\])
\[ matches the character [ with index 9110 (5B16 or 1338) literally (case sensitive)
2nd Capturing Group
(\d+|(?:\d*\.\d+))
1st Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
(?:\d*\.\d+)
Non-capturing group
(?:\d*\.\d+)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:,\s*(\d+|(?:\d*\.\d+)))*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
, matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
3rd Capturing Group
(\d+|(?:\d*\.\d+))
1st Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
(?:\d*\.\d+)
Non-capturing group
(?:\d*\.\d+)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\] matches the character ] with index 9310 (5D16 or 1358) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\*x]
\* matches the character * with index 4210 (2A16 or 528) literally (case sensitive)
x matches the character x with index 12010 (7816 or 1708) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
4th Capturing Group
(\[(\d+|(?:\d*\.\d+))(?:,\s*(\d+|(?:\d*\.\d+)))*\])
\[ matches the character [ with index 9110 (5B16 or 1338) literally (case sensitive)
5th Capturing Group
(\d+|(?:\d*\.\d+))
1st Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
(?:\d*\.\d+)
Non-capturing group
(?:\d*\.\d+)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:,\s*(\d+|(?:\d*\.\d+)))*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
, matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v \u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
6th Capturing Group
(\d+|(?:\d*\.\d+))
1st Alternative
\d+
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
(?:\d*\.\d+)
Non-capturing group
(?:\d*\.\d+)
\d
matches a digit (equivalent to [0-9])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\] matches the character ] with index 9310 (5D16 or 1358) literally (case sensitive)
$ 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.

Regular Expression
No Match

/
/
gm

Test String