When is {{- the dash used?

I have an env variable

env:

- name: POD_NAME

valueFrom:

fieldRef:

fieldPath: metadata.name

Now I want to modify the POD_NAME and pass it as a variable to the container , something like

- --partition-number

- {{ (splitList “-” PODNAME) | last | quote }}

but it doesnt work. I am trying tot think what am I missing