Change variable group name dynamically in azure devops using a variable

In my case I wanted to determine proper variable group based on a value of variable defined for specific pipeline. The goal was to avoid the need to have separate yml file for each environment. First, I tried following syntax:

variables:
- ${{ if eq(variables['EnvName'], 'prod') }}:
  - group: prod

but if expression seems to be evaluated compile time and at that moment values of the variables are not yet set so it didn't work.

Instead I used one of the "build variables" which luckily are already set when if expression is processed. For me DefinitionName variable which returns the name of the build pipeline was a good candidate as I have environment specified in my pipelines' names:

This is what I used in the yml:

variables:
- ${{ if contains(variables['Build.DefinitionName'], 'testing') }}:
  - group: testing-env-group
- ${{ elseif contains(variables['Build.DefinitionName'], 'staging') }}:
  - group: staging-env-group
- ${{ elseif contains(variables['Build.DefinitionName'], 'production') }}:
  - group: prod-env-group

As mentioned in this answer, you don't need the conditions to evaluate the variable group. Below is a complete working YAML that uses variables instead of parameters

trigger: none
 
variables:
- name: env
  value: 'Staging'
- group: ${{ variables.env }}

pool:
  vmImage: ubuntu-latest

jobs:
- job: Build
  steps:
  - script: echo Environment is $(env)

Demo Run: