Looks to be doing what i want here

.woodpecker.yml

@@ -0,0 +1,13 @@
+steps:
+  build:
+    image: woodpeckerci/plugin-docker-buildx:2
+    settings:
+      debug: "true"
+      repo: "gitea.simcop2387.info/simcop2387/docker-perl-dind"
+      auto_tag: "true"
+      logins:
+        - registry: https://gitea.simcop2387.info/
+          username: simcop2387
+          password:
+            from_secret: gitea_docker_token
+

Dockerfile

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+FROM docker:dind-rootless
+USER root
+RUN apk update && apk add perl curl bash build-base
+USER rootless
+RUN curl -L https://install.perlbrew.pl | bash
+RUN bash -c 'source $HOME/perl5/perlbrew/etc/bashrc; perlbrew init && perlbrew install --verbose perl-5.38.0 && perlbrew switch perl-5.38.0 && perlbrew install-cpanm && wget https://gitea.simcop2387.info/simcop2387/docker-perl/raw/branch/master/cpanfile && cpanm --installdeps && rm cpanfile'

README.md

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+This builds a copy of the docker dind with a modern perl install at the same time
+
+