To prevent that, you need a negative look-ahead:
No, you don't. 
$_ = "[[foo]] bar [[baz ] qux]] [quux]] fred [[waldo]]]";
say $1 while /\[\[([^]]*(?:\][^]]+)*)\]\]/g;
__END__
foo
baz ] qux
waldo

[download]
This uses some classical loop-unrolling, and is, IIRC, similar how Mastering Regular Expressions (first edition) matches C comments.

In reply to Re^2: Regex question - negatives by JavaFan
in thread Regex question - negatives by ultranerds

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