I am using very short snippet of groovy code in my build step (bash script) to retrieve and set variable. I have a variable defined in configuration which value I can easily retrieve using the short groovy code.

${vars.getValue("var_name")}

If I want to set static string as a new value for this variable I can do it like this:

${vars.get("var_name").setValue("NEW VALUE")}

This static string works OK!!!
But if I want to use in setValue method some other variable which is previously defined in this Step with bash script:

file_name="NEW VALUE"
${vars.get("var_name").setValue($file_name)}

I am getting an error:

ERROR - Step 'master>lin_download_artifactory' is failed: Failed to evaluate below expression in configuration 'root/arena':
mvel:vars.get("var_name").setValue($file_name)

I tried as well:

${vars.get("var_name").setValue(file_name)}

The same** ERROR!**

Can you please tell me how I could reference variable within the setValue method? I tried also setValue(file_name) but it doesn't work as well.