Regular Expressions 101

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/
([EI][XN]T\. \D*)(\d*)\s*(\d.*)
/
gm
1st Capturing Group
([EI][XN]T\. \D*)
Match a single character present in the list below
[EI]
EI
matches a single character in the list EI (case sensitive)
Match a single character present in the list below
[XN]
XN
matches a single character in the list XN (case sensitive)
T matches the character T with index 8410 (5416 or 1248) literally (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
\D
matches any character that's not 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)
2nd Capturing Group
(\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)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
3rd Capturing Group
(\d.*)
\d matches a digit (equivalent to [0-9])
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
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.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String