How can we change two values dynamically by using one variable? in yaml script?

Question

we are using gitlab for ci/cd we have two branches for frontend dev branch-

workflow:
  rules:
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH || $CI_COMMIT_BRANCH == "dev" || $CI_COMMIT_BRANCH == "uat"
      when: always
    - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH || $CI_COMMIT_BRANCH != "dev" || $CI_COMMIT_BRANCH != "uat"
      when: never 

default:
  image: node:xx.xx.x

stages:
  - build
  - deploy

build:
  stage: build
  script: 
    - npm i
    - npm run build:dev
  only:
    - dev
    - merge_requests
  artifacts:
    paths:
      - build

deploy:
  stage: deploy
  image:
    name: amazon/aws-cli
    entrypoint: [""]
  script:
    - aws --version
    - aws s3 rm s3://XXXXXXXXXXX-dev-operation-portal --recursive
    - aws s3 cp build s3://XXXXXXXXXXXX-dev-operation-portal --acl public-read --recursive
    - aws cloudfront create-invalidation --distribution-id=**XXXXXXXXXXXX** --paths "/*"
  only:
    - dev
    - merge_requests

Uat branch

workflow:
  rules:
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH || $CI_COMMIT_BRANCH == "dev" || $CI_COMMIT_BRANCH == "uat"
      when: always
    - if: $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH || $CI_COMMIT_BRANCH != "dev" || $CI_COMMIT_BRANCH != "uat"
      when: never 

default:
  image: node:xx.x.x

stages:
  - build
  - deploy

build:
  stage: build
  script: 
    - npm i
    - npm run build:uat
  only:
    - dev
    - merge_requests
  artifacts:
    paths:
      - build

deploy:
  stage: deploy
  image:
    name: amazon/aws-cli
    entrypoint: [""]
  script:
    - aws --version
    - aws s3 rm s3://XXXXXXXXXXX-uat-operation-portal --recursive
    - aws s3 cp build s3://XXXXXXXXXXXX-uat-operation-portal --acl public-read --recursive
    - aws cloudfront create-invalidation --distribution-id=**XXXXXXXXXXXX** --paths "/*"
  only:
    - uat
    - merge_requests

Like here I'm using dev branch.While merging dev to uat- conflicts done, fully interchanged ,the dev content changed to the uat. But in future case,it is difficult for deployment, again in uat, we are changing the script to dev. So ,now I want common variable name, what are the names comes under dev or uat , they have a common variable like for eg: $branch .and also there is distribution id , there also I need a common variable like for eg: $distribution_id .Now I want we are having one variable($branch) with two values(dev or uat) How to change the value, if it runs in uat, uat should trigger to the value. If it runs in dev, dev should trigger to the value as same as distribution id. How can we interchange these variables according to the branch .(dynamic variable)