Regular Expressions 101

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/
^([\w.]+\.)\s+.+\sNS\s.+\1
/
^ asserts position at start of the string
1st Capturing Group
([\w.]+\.)
Match a single character present in the list below
[\w.]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\w matches any word character (equivalent to [a-zA-Z0-9_])
. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
.
matches any character (except for line terminators)
+ matches the previous token between one 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 ])
NS
matches the characters NS literally (case sensitive)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
.
matches any character (except for line terminators)
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\1 matches the same text as most recently matched by the 1st capturing group
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/

Test String