Regular Expressions 101

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/
<a(?:.*\>)(.*)<\/a>
/
ig
<a
matches the characters <a literally (case insensitive)
Non-capturing group
(?:.*\>)
.
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)
\> matches the character > with index 6210 (3E16 or 768) literally (case insensitive)
1st Capturing Group
(.*)
.
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)
< matches the character < with index 6010 (3C16 or 748) literally (case insensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case insensitive)
a>
matches the characters a> literally (case insensitive)
Global pattern flags
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/
ig

Test String