The minimum the regex can match is a $ because the second capture is optional. If there are no \w characters following a $ character then the second capture will be undef and you get the warning. There are two ways you can fix it depending on the desired result. Using

(\$(\w+))

[download]

prints '$Word $' for the sample line, and

(\$(\w*))

[download]

prints '$Word dollar'.

True laziness is hard work

In reply to Re: Use of uninitialized value in concatenation by GrandFather
in thread Use of uninitialized value in concatenation by gem555

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