capture optional surrounding characters

Question

I'm not that savvy in regex, so I'm not sure how to achieve the following thing:

I'd like to capture any arbitary string from an input that may or may not be surrounded by the '$' character. If a '$' character is present at the beginning of the string, the '$' character at the end must be present.

Currently I have

^\w+([_.-]\w+)*$

which roughly translates to:

1. Arbitary word characters
2. Beginning of capture group
3. any character of '_', '.', '-'
4. Before an optional \\n

So valid matches would be:

test
test-5
test.1.3
test-alpha.2

Now I'd like to make this possible

$test$

But not...

$test (or test$)

Answer 1

^(?:(?:\w+(?:[_.-]\w+)*)|\$test\$)$

Its better to add that with | instead off modifying the original one.See demo.

https://regex101.com/r/wU7sQ0/32