Regular Expressions 101

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/
<\?.*[\s\S]*?(?:$|\?\>)
/
g
< matches the character < with index 6010 (3C16 or 748) literally (case sensitive)
\? matches the character ? with index 6310 (3F16 or 778) literally (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\s\S]
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
\S matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
Non-capturing group
(?:$|\?\>)
1st Alternative
$
$ asserts position at the end of the string, or before the line terminator right at the end of the string (if any)
2nd Alternative
\?\>
\? matches the character ? with index 6310 (3F16 or 778) literally (case sensitive)
\> matches the character > with index 6210 (3E16 or 768) literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

Test String