Struggling with regex in Layer Name Editor

[keung office24362655u5zi]

[^_]*$
Using the above expression to select the characters after "_"
but if the layer name has two more "_" then only the characters after the latest "_" will be selected

I tried another expression (?<=_).* but it doesn't work

Help~~~

[Stephen_A_Marsh]

Which script? Can you point to the code?

Can you show an example of the layers panel?

Is the string something like:

_layer name
__layer name

___layer name

Edit: Edit is it something like this animation?

[keung office24362655u5zi]

I find out the problem is  Lookahead not being supported
(?<=_).*

[keung office24362655u5zi]

The layer panel is here

[Stephen_A_Marsh]

Thanks, it is still not clear what script or panel or code is being used?

A before and after rename would also be helpful.

[keung office24362655u5zi]

I use this one (?=_)(.*) instead of  (?<=_).*, then it works