Regular Expressions 101

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/
^(?!\s*^(#.*|_.*|pkgname|depends)=)[^\s=-]+=
/
gm
^ asserts position at start of a line
Negative Lookahead
(?!\s*^(#.*|_.*|pkgname|depends)=)
Assert that the Regex below does not match
\s
matches any whitespace character (equivalent to [\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
^ asserts position at start of a line
1st Capturing Group
(#.*|_.*|pkgname|depends)
1st Alternative
#.*
# matches the character # with index 3510 (2316 or 438) literally (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Alternative
_.*
_ matches the character _ with index 9510 (5F16 or 1378) literally (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
3rd Alternative
pkgname
pkgname
matches the characters pkgname literally (case sensitive)
4th Alternative
depends
depends
matches the characters depends literally (case sensitive)
= matches the character = with index 6110 (3D16 or 758) 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 a single character in the list =- (case sensitive)
= matches the character = with index 6110 (3D16 or 758) literally (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.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String