Regular Expressions 101

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"
\b(10[.][0-9]{4,}(?:[.][0-9]+)*/(?:(?![\"&\'<>];)\S)+)\b
"
gm
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
1st Capturing Group
(10[.][0-9]{4,}(?:[.][0-9]+)*/(?:(?![\"&\'<>];)\S)+)
10
matches the characters 10 literally (case sensitive)
Match a single character present in the list below
[.]
. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9]
{4,} matches the previous token between 4 and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
Non-capturing group
(?:[.][0-9]+)*
* 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
[.]
. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
Non-capturing group
(?:(?![\"&\'<>];)\S)+
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Negative Lookahead
(?![\"&\'<>];)
Assert that the Regex below does not match
Match a single character present in the list below
[\"&\'<>]
\" matches the character " with index 3410 (2216 or 428) literally (case sensitive)
& matches the character & with index 3810 (2616 or 468) literally (case sensitive)
\' matches the character ' with index 3910 (2716 or 478) literally (case sensitive)
<>
matches a single character in the list <> (case sensitive)
; matches the character ; with index 5910 (3B16 or 738) literally (case sensitive)
\S matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
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.

Regular Expression
No Match

r"
"
gm

Test String