diff --git a/3.1-rc/alpine3.13/Dockerfile b/3.1-rc/alpine3.13/Dockerfile
new file mode 100644
index 000000000..2073ef1d1
--- /dev/null
+++ b/3.1-rc/alpine3.13/Dockerfile
@@ -0,0 +1,141 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM alpine:3.13
+
+RUN set -eux; \
+	apk add --no-cache \
+		bzip2 \
+		ca-certificates \
+		gmp-dev \
+		libffi-dev \
+		procps \
+		yaml-dev \
+		zlib-dev \
+	;
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+# readline-dev vs libedit-dev: https://bugs.ruby-lang.org/issues/11869 and https://github.com/docker-library/ruby/issues/75
+	apk add --no-cache --virtual .ruby-builddeps \
+		autoconf \
+		bison \
+		bzip2 \
+		bzip2-dev \
+		ca-certificates \
+		coreutils \
+		dpkg-dev dpkg \
+		g++ \
+		gcc \
+		gdbm-dev \
+		glib-dev \
+		libc-dev \
+		libffi-dev \
+		libxml2-dev \
+		libxslt-dev \
+		linux-headers \
+		make \
+		ncurses-dev \
+		openssl \
+		openssl-dev \
+		patch \
+		procps \
+		readline-dev \
+		ruby \
+		tar \
+		xz \
+		yaml-dev \
+		zlib-dev \
+	; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# https://github.com/docker-library/ruby/issues/196
+# https://bugs.ruby-lang.org/issues/14387#note-13 (patch source)
+# https://bugs.ruby-lang.org/issues/14387#note-16 ("Therefore ncopa's patch looks good for me in general." -- only breaks glibc which doesn't matter here)
+	wget -O 'thread-stack-fix.patch' 'https://bugs.ruby-lang.org/attachments/download/7081/0001-thread_pthread.c-make-get_main_stack-portable-on-lin.patch'; \
+	echo '3ab628a51d92fdf0d2b5835e93564857aea73e0c1de00313864a94a6255cb645 *thread-stack-fix.patch' | sha256sum --check --strict; \
+	patch -p1 -i thread-stack-fix.patch; \
+	rm thread-stack-fix.patch; \
+	\
+# the configure script does not detect isnan/isinf as macros
+	export ac_cv_func_isnan=yes ac_cv_func_isinf=yes; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	runDeps="$( \
+		scanelf --needed --nobanner --format '%n#p' --recursive /usr/local \
+			| tr ',' '\n' \
+			| sort -u \
+			| awk 'system("[ -e /usr/local/lib/" $1 " ]") == 0 { next } { print "so:" $1 }' \
+	)"; \
+	apk add --no-network --virtual .ruby-rundeps $runDeps; \
+	apk del --no-network .ruby-builddeps; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if \
+		apk --no-network list --installed \
+			| grep -v '^[.]ruby-rundeps' \
+			| grep -i ruby \
+	; then \
+		exit 1; \
+	fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/3.1-rc/alpine3.14/Dockerfile b/3.1-rc/alpine3.14/Dockerfile
new file mode 100644
index 000000000..62d9ed032
--- /dev/null
+++ b/3.1-rc/alpine3.14/Dockerfile
@@ -0,0 +1,141 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM alpine:3.14
+
+RUN set -eux; \
+	apk add --no-cache \
+		bzip2 \
+		ca-certificates \
+		gmp-dev \
+		libffi-dev \
+		procps \
+		yaml-dev \
+		zlib-dev \
+	;
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+# readline-dev vs libedit-dev: https://bugs.ruby-lang.org/issues/11869 and https://github.com/docker-library/ruby/issues/75
+	apk add --no-cache --virtual .ruby-builddeps \
+		autoconf \
+		bison \
+		bzip2 \
+		bzip2-dev \
+		ca-certificates \
+		coreutils \
+		dpkg-dev dpkg \
+		g++ \
+		gcc \
+		gdbm-dev \
+		glib-dev \
+		libc-dev \
+		libffi-dev \
+		libxml2-dev \
+		libxslt-dev \
+		linux-headers \
+		make \
+		ncurses-dev \
+		openssl \
+		openssl-dev \
+		patch \
+		procps \
+		readline-dev \
+		ruby \
+		tar \
+		xz \
+		yaml-dev \
+		zlib-dev \
+	; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# https://github.com/docker-library/ruby/issues/196
+# https://bugs.ruby-lang.org/issues/14387#note-13 (patch source)
+# https://bugs.ruby-lang.org/issues/14387#note-16 ("Therefore ncopa's patch looks good for me in general." -- only breaks glibc which doesn't matter here)
+	wget -O 'thread-stack-fix.patch' 'https://bugs.ruby-lang.org/attachments/download/7081/0001-thread_pthread.c-make-get_main_stack-portable-on-lin.patch'; \
+	echo '3ab628a51d92fdf0d2b5835e93564857aea73e0c1de00313864a94a6255cb645 *thread-stack-fix.patch' | sha256sum --check --strict; \
+	patch -p1 -i thread-stack-fix.patch; \
+	rm thread-stack-fix.patch; \
+	\
+# the configure script does not detect isnan/isinf as macros
+	export ac_cv_func_isnan=yes ac_cv_func_isinf=yes; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	runDeps="$( \
+		scanelf --needed --nobanner --format '%n#p' --recursive /usr/local \
+			| tr ',' '\n' \
+			| sort -u \
+			| awk 'system("[ -e /usr/local/lib/" $1 " ]") == 0 { next } { print "so:" $1 }' \
+	)"; \
+	apk add --no-network --virtual .ruby-rundeps $runDeps; \
+	apk del --no-network .ruby-builddeps; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if \
+		apk --no-network list --installed \
+			| grep -v '^[.]ruby-rundeps' \
+			| grep -i ruby \
+	; then \
+		exit 1; \
+	fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/3.1-rc/bullseye/Dockerfile b/3.1-rc/bullseye/Dockerfile
new file mode 100644
index 000000000..a07021315
--- /dev/null
+++ b/3.1-rc/bullseye/Dockerfile
@@ -0,0 +1,95 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM buildpack-deps:bullseye
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bison \
+		dpkg-dev \
+		libgdbm-dev \
+		ruby \
+	; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	apt-mark auto '.*' > /dev/null; \
+	apt-mark manual $savedAptMark > /dev/null; \
+	find /usr/local -type f -executable -not \( -name '*tkinter*' \) -exec ldd '{}' ';' \
+		| awk '/=>/ { print $(NF-1) }' \
+		| sort -u \
+		| grep -vE '^/usr/local/lib/' \
+		| xargs -r dpkg-query --search \
+		| cut -d: -f1 \
+		| sort -u \
+		| xargs -r apt-mark manual \
+	; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if dpkg -l | grep -i ruby; then exit 1; fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/3.1-rc/buster/Dockerfile b/3.1-rc/buster/Dockerfile
new file mode 100644
index 000000000..b6c08a6df
--- /dev/null
+++ b/3.1-rc/buster/Dockerfile
@@ -0,0 +1,95 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM buildpack-deps:buster
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bison \
+		dpkg-dev \
+		libgdbm-dev \
+		ruby \
+	; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	apt-mark auto '.*' > /dev/null; \
+	apt-mark manual $savedAptMark > /dev/null; \
+	find /usr/local -type f -executable -not \( -name '*tkinter*' \) -exec ldd '{}' ';' \
+		| awk '/=>/ { print $(NF-1) }' \
+		| sort -u \
+		| grep -vE '^/usr/local/lib/' \
+		| xargs -r dpkg-query --search \
+		| cut -d: -f1 \
+		| sort -u \
+		| xargs -r apt-mark manual \
+	; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if dpkg -l | grep -i ruby; then exit 1; fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/3.1-rc/slim-bullseye/Dockerfile b/3.1-rc/slim-bullseye/Dockerfile
new file mode 100644
index 000000000..0193663af
--- /dev/null
+++ b/3.1-rc/slim-bullseye/Dockerfile
@@ -0,0 +1,122 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM debian:bullseye-slim
+
+RUN set -eux; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bzip2 \
+		ca-certificates \
+		libffi-dev \
+		libgmp-dev \
+		libssl-dev \
+		libyaml-dev \
+		procps \
+		zlib1g-dev \
+	; \
+	rm -rf /var/lib/apt/lists/*
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bison \
+		dpkg-dev \
+		libgdbm-dev \
+		ruby \
+		autoconf \
+		g++ \
+		gcc \
+		libbz2-dev \
+		libgdbm-compat-dev \
+		libglib2.0-dev \
+		libncurses-dev \
+		libreadline-dev \
+		libxml2-dev \
+		libxslt-dev \
+		make \
+		wget \
+		xz-utils \
+	; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	apt-mark auto '.*' > /dev/null; \
+	apt-mark manual $savedAptMark > /dev/null; \
+	find /usr/local -type f -executable -not \( -name '*tkinter*' \) -exec ldd '{}' ';' \
+		| awk '/=>/ { print $(NF-1) }' \
+		| sort -u \
+		| grep -vE '^/usr/local/lib/' \
+		| xargs -r dpkg-query --search \
+		| cut -d: -f1 \
+		| sort -u \
+		| xargs -r apt-mark manual \
+	; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if dpkg -l | grep -i ruby; then exit 1; fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/3.1-rc/slim-buster/Dockerfile b/3.1-rc/slim-buster/Dockerfile
new file mode 100644
index 000000000..433e624a8
--- /dev/null
+++ b/3.1-rc/slim-buster/Dockerfile
@@ -0,0 +1,122 @@
+#
+# NOTE: THIS DOCKERFILE IS GENERATED VIA "apply-templates.sh"
+#
+# PLEASE DO NOT EDIT IT DIRECTLY.
+#
+
+FROM debian:buster-slim
+
+RUN set -eux; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bzip2 \
+		ca-certificates \
+		libffi-dev \
+		libgmp-dev \
+		libssl-dev \
+		libyaml-dev \
+		procps \
+		zlib1g-dev \
+	; \
+	rm -rf /var/lib/apt/lists/*
+
+# skip installing gem documentation
+RUN set -eux; \
+	mkdir -p /usr/local/etc; \
+	{ \
+		echo 'install: --no-document'; \
+		echo 'update: --no-document'; \
+	} >> /usr/local/etc/gemrc
+
+ENV LANG C.UTF-8
+ENV RUBY_MAJOR 3.1-rc
+ENV RUBY_VERSION 3.1.0-preview1
+ENV RUBY_DOWNLOAD_SHA256 86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d
+
+# some of ruby's build scripts are written in ruby
+#   we purge system ruby later to make sure our final image uses what we just built
+RUN set -eux; \
+	\
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends \
+		bison \
+		dpkg-dev \
+		libgdbm-dev \
+		ruby \
+		autoconf \
+		g++ \
+		gcc \
+		libbz2-dev \
+		libgdbm-compat-dev \
+		libglib2.0-dev \
+		libncurses-dev \
+		libreadline-dev \
+		libxml2-dev \
+		libxslt-dev \
+		make \
+		wget \
+		xz-utils \
+	; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz"; \
+	echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum --check --strict; \
+	\
+	mkdir -p /usr/src/ruby; \
+	tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1; \
+	rm ruby.tar.xz; \
+	\
+	cd /usr/src/ruby; \
+	\
+# hack in "ENABLE_PATH_CHECK" disabling to suppress:
+#   warning: Insecure world writable dir
+	{ \
+		echo '#define ENABLE_PATH_CHECK 0'; \
+		echo; \
+		cat file.c; \
+	} > file.c.new; \
+	mv file.c.new file.c; \
+	\
+	autoconf; \
+	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
+	./configure \
+		--build="$gnuArch" \
+		--disable-install-doc \
+		--enable-shared \
+	; \
+	make -j "$(nproc)"; \
+	make install; \
+	\
+	apt-mark auto '.*' > /dev/null; \
+	apt-mark manual $savedAptMark > /dev/null; \
+	find /usr/local -type f -executable -not \( -name '*tkinter*' \) -exec ldd '{}' ';' \
+		| awk '/=>/ { print $(NF-1) }' \
+		| sort -u \
+		| grep -vE '^/usr/local/lib/' \
+		| xargs -r dpkg-query --search \
+		| cut -d: -f1 \
+		| sort -u \
+		| xargs -r apt-mark manual \
+	; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	\
+	cd /; \
+	rm -r /usr/src/ruby; \
+# verify we have no "ruby" packages installed
+	if dpkg -l | grep -i ruby; then exit 1; fi; \
+	[ "$(command -v ruby)" = '/usr/local/bin/ruby' ]; \
+# rough smoke test
+	ruby --version; \
+	gem --version; \
+	bundle --version
+
+# don't create ".bundle" in all our apps
+ENV GEM_HOME /usr/local/bundle
+ENV BUNDLE_SILENCE_ROOT_WARNING=1 \
+	BUNDLE_APP_CONFIG="$GEM_HOME"
+ENV PATH $GEM_HOME/bin:$PATH
+# adjust permissions of a few directories for running "gem install" as an arbitrary user
+RUN mkdir -p "$GEM_HOME" && chmod 777 "$GEM_HOME"
+
+CMD [ "irb" ]
diff --git a/versions.json b/versions.json
index c428c8c02..863edff1f 100644
--- a/versions.json
+++ b/versions.json
@@ -34,5 +34,17 @@
       "alpine3.13"
     ],
     "version": "3.0.2"
+  },
+  "3.1-rc": {
+    "sha256": "86a836ad42f6a7a469fce71ffec48fd3184af55bf79e488b568a4f64adee551d",
+    "variants": [
+      "bullseye",
+      "slim-bullseye",
+      "buster",
+      "slim-buster",
+      "alpine3.14",
+      "alpine3.13"
+    ],
+    "version": "3.1.0-preview1"
   }
 }