How to extract a value between to identifiers?

[wantjoule]

I'm looking for a way to extract a value from the middle of a sting. The value(green) I want is after the first underscore(blue) and before the dash(pink)

Example:

GET_tres_main.aspx_detail_showall-0

[ITWhisperer · Accepted solution]

With a limited example, this may not be enough

| rex "GET_(?<value>[^\-]+)"