Regular Expressions 101

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/
((\<ref\>)(.)(?=\/\/)\/\/(.)(?=\/)(.)(?=\<\/ref>)(\<\/ref\>))((.|\n)*?)(?=\1)(\1)
/
gm
1st Capturing Group
((\<ref\>)(.)(?=\/\/)\/\/(.)(?=\/)(.)(?=\<\/ref>)(\<\/ref\>))
2nd Capturing Group
(\<ref\>)
\< matches the character < literally (case sensitive)
ref matches the characters ref literally (case sensitive)
\> matches the character > literally (case sensitive)
3rd Capturing Group
(.)
.
matches any character (except for line terminators)
+? matches the previous token between one and unlimited times, as few times as possible, expanding as needed (lazy)
Positive Lookahead
(?=\/\/)
Assert that the Regex below matches
\/ matches the character / literally (case sensitive)
\/ matches the character / literally (case sensitive)
\/ matches the character / literally (case sensitive)
\/ matches the character / literally (case sensitive)
4th Capturing Group
(.)
.
matches any character (except for line terminators)
Positive Lookahead
(?=\/)
Assert that the Regex below matches
\/ matches the character / literally (case sensitive)
5th Capturing Group
(.)
Positive Lookahead
(?=\<\/ref>)
Assert that the Regex below matches
6th Capturing Group
(\<\/ref\>)
7th Capturing Group
((.|\n)*?)
8th Capturing Group
(.|\n)*?
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
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 non-capturing group instead if you're not interested in the data
1st Alternative
.
. matches any character (except for line terminators)
2nd Alternative
\n
\n matches a line-feed (newline) character (ASCII 10)
Positive Lookahead
(?=\1)
Assert that the Regex below matches
\1 matches the same text as most recently matched by the 1st capturing group
9th Capturing Group
(\1)
\1 matches the same text as most recently matched by the 1st capturing group
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

Substitution

Processing...