Regular Expressions 101

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;
^http(s?)\:\/\/[^\s\/$.?#*]+\.[^\s\/$.?#*]+(\.[^\s\/$.?#*]+)*$
;
gm
^ asserts position at start of a line
http
matches the characters http literally (case sensitive)
1st Capturing Group
(s?)
s
matches the character s with index 11510 (7316 or 1638) literally (case sensitive)
\: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
Match a single character not present in the list below
[^\s\/$.?#*]
+ 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 ])
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
$.?#*
matches a single character in the list $.?#* (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character not present in the list below
[^\s\/$.?#*]
+ 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 ])
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
$.?#*
matches a single character in the list $.?#* (case sensitive)
2nd Capturing Group
(\.[^\s\/$.?#*]+)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
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
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character not present in the list below
[^\s\/$.?#*]
+ 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 ])
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
$.?#*
matches a single character in the list $.?#* (case sensitive)
$ asserts position at the end of a line
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