add unit tests

.woodpecker/build.yaml

@@ -0,0 +1,21 @@
+matrix:
+  include:
+    # - image: perl:5.36.0-slim-bullseye
+    # - image: perl:5.38.0-slim-bookworm
+    # - image: perl:5.40.0-slim-bookworm
+    # - image: perl:5.42.0-slim-bookworm
+    - image: perl:5.43.5-slim-bookworm
+
+steps:
+  test:
+    when:
+      event: [push]
+    image: ${image}
+    commands:
+      - subst -r 's/2025/foobar/' t/file*
+      - grep foobar t/file*
+      - cp t/file1 t/huh.1
+      - cp t/file1 t/mor.2
+      - subst -m 's/(huh|mor)/sub/g' '/.\d$/'
+      - ls -l t/sub.1
+      - ls -l t/sub.2