diff --git a/.github/workflows/pr.yaml b/.github/workflows/pr.yaml
index 52073b6..12cf21c 100644
--- a/.github/workflows/pr.yaml
+++ b/.github/workflows/pr.yaml
@@ -35,15 +35,23 @@ jobs:
         with:
           go-version-file: ./go.mod
 
+      # What the pull request's author writes (its title, its branch, its
+      # login) reaches the script as environment variables, never spliced
+      # into it: an expression in a script is text in the script.
       - name: Summary Information
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_AUTHOR: ${{ github.event.pull_request.user.login }}
+          PR_HEAD: ${{ github.event.pull_request.head.ref }}
+          PR_BASE: ${{ github.event.pull_request.base.ref }}
         run: |
           echo "# Pull Request Summary" > $GITHUB_STEP_SUMMARY
           echo "" >> $GITHUB_STEP_SUMMARY
           echo "**Repository:** ${{ github.repository }}" >> $GITHUB_STEP_SUMMARY
-          echo "**Pull Request:** ${{ github.event.pull_request.title }}" >> $GITHUB_STEP_SUMMARY
-          echo "**Author:** ${{ github.event.pull_request.user.login }}" >> $GITHUB_STEP_SUMMARY
-          echo "**Branch:** ${{ github.event.pull_request.head.ref }}" >> $GITHUB_STEP_SUMMARY
-          echo "**Base:** ${{ github.event.pull_request.base.ref }}" >> $GITHUB_STEP_SUMMARY
+          echo "**Pull Request:** ${PR_TITLE}" >> $GITHUB_STEP_SUMMARY
+          echo "**Author:** ${PR_AUTHOR}" >> $GITHUB_STEP_SUMMARY
+          echo "**Branch:** ${PR_HEAD}" >> $GITHUB_STEP_SUMMARY
+          echo "**Base:** ${PR_BASE}" >> $GITHUB_STEP_SUMMARY
           echo "**Commits:** ${{ github.event.pull_request.commits }}" >> $GITHUB_STEP_SUMMARY
           echo "**Changed Files:** ${{ github.event.pull_request.changed_files }}" >> $GITHUB_STEP_SUMMARY
           echo "**Additions:** ${{ github.event.pull_request.additions }}" >> $GITHUB_STEP_SUMMARY