Regular Expressions 101

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"
(/?ark:/? ?)([-a-zA-Z0-9@:%_\+.~#?&//=]*)
"
gm
1st Capturing Group
(/?ark:/? ?)
/
matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
ark:
matches the characters ark: literally (case sensitive)
/
matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
2nd Capturing Group
([-a-zA-Z0-9@:%_\+.~#?&//=]*)
Match a single character present in the list below
[-a-zA-Z0-9@:%_\+.~#?&//=]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
@:%_
matches a single character in the list @:%_ (case sensitive)
\+ matches the character + with index 4310 (2B16 or 538) literally (case sensitive)
.~#?&//=
matches a single character in the list .~#?&/= (case sensitive)
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