diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index eabcabb..35aa985 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,13 +1,99 @@
 name: CI
 on: push
 jobs:
+  # # No build matrix stage
+  # setup-python:
+  #   strategy:
+  #     matrix:
+  #       os: [ubuntu-latest]
+  #       python-version: ['3.8', '3.9', '3.10']
+  #   runs-on: ${{ matrix.os }}
+  #   steps:
+  #     - run: |
+  #         echo "black" >> requirements.txt
+  #         echo "pylint" >> requirements.txt
+  #         echo "pytest" >> requirements.txt
+  #     - uses: actions/setup-python@v4
+  #       with:
+  #         python-version: '${{ matrix.python-version }}'
+  #         cache: pip
+  #     - run: python --version
+  #     - run: python -m pip install -r requirements.txt
+  #     - run: python -m pip list
+  # check-code:
+  #   needs: setup-python
+  #   strategy:
+  #     matrix:
+  #       os: [ubuntu-latest]
+  #       python-version: ['3.8', '3.9', '3.10']
+  #   runs-on: ${{ matrix.os }}
+  #   steps:
+  #     - run: |
+  #         echo "black" >> requirements.txt
+  #         echo "pylint" >> requirements.txt
+  #         echo "pytest" >> requirements.txt
+  #     - uses: actions/setup-python@v4
+  #       with:
+  #         python-version: '${{ matrix.python-version }}'
+  #         cache: pip
+  #     - run: python -m pip install -r requirements.txt
+  #     - run: black --check .
+  #     - run: pylint .
+  # unit-test:
+  #   needs: setup-python
+  #   strategy:
+  #     matrix:
+  #       os: [ubuntu-latest]
+  #       python-version: ['3.8', '3.9', '3.10']
+  #   runs-on: ${{ matrix.os }}
+  #   steps:
+  #     - run: |
+  #         echo "black" >> requirements.txt
+  #         echo "pylint" >> requirements.txt
+  #         echo "pytest" >> requirements.txt
+  #     - uses: actions/setup-python@v4
+  #       with:
+  #         python-version: '${{ matrix.python-version }}'
+  #         cache: pip
+  #     - run: python -m pip install -r requirements.txt
+  #     - run: pytest
+
   build-matrix:
     name: '🧱 Build matrix'
     runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.build-matrix.outputs.matrix }}
     steps:
       - name: Checkout code
         uses: actions/checkout@v3
       - name: '🧱 Build matrix'
         id: build-matrix
         uses: ./
-      - run: echo "${{ steps.build-matrix.outputs.matrix }}"
+        with:
+          matrix: |
+            os: ubuntu-latest windows-latest macos-latest,
+            node-version: 16 18,
+            python-version: 3.6 3.8 3.10 3.12
+  test-matrix:
+    name: '🧪 Test matrix'
+    needs:
+      - build-matrix
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: '📢 Echo matrix combination'
+        run: |
+          echo "${{ matrix.os }}"
+          echo "${{ matrix.node-version }}"
+          echo "${{ matrix.python-version }}"
+
+  # debug-matrix:
+  #   strategy:
+  #     matrix:
+  #       foo: [a, b, c]
+  #       bar: [a, b, a]
+  #   runs-on: ubuntu-latest
+  #   steps:
+  #     - run: echo "a=${{ matrix.a }}, b=${{ matrix.b }}"
diff --git a/.gitignore b/.gitignore
index 9e27a53..489cd11 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 .vscode/
 .idea/
 .direnv/
+.dev/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 8244b3c..c318f43 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -11,6 +11,8 @@ repos:
       - id: check-added-large-files
       - id: check-merge-conflict
       - id: check-yaml
+      - id: check-executables-have-shebangs
+
   - repo: https://github.com/pre-commit/mirrors-prettier
     rev: v2.7.1
     hooks:
@@ -20,3 +22,8 @@ repos:
     hooks:
       - id: check-github-actions
       - id: check-github-workflows
+  - repo: https://github.com/jumanjihouse/pre-commit-hooks
+    rev: 3.0.0
+    hooks:
+      - id: shellcheck
+      - id: shfmt
diff --git a/README.md b/README.md
index 971875e..7ff21e0 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,352 @@
 # Build Matrix
 
-GitHub action to create a reusable and potentially dynamic matrix for workflow jobs.
+GitHub action to create reusable dynamic job matrices for your workflows.
+
+This action adresses a wide known problem of reusing the same job matrix
+multiple times or even generating a matrix on the fly.
+
+The main goal of this action is to be as much compatible with built-in
+[GitHub matrices](https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs)
+as possible and thus allow you a smooth transition in your workflow.
+
+## Basic usage
+
+```yaml
+jobs:
+  # Build matrix
+  build-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.build.outputs.matrix }}
+    steps:
+      - id: build
+        uses: druzsan/build-matrix@v1
+        with:
+          matrix: |
+            os: ubuntu-latest windows-latest macos-latest,
+            python-version: 3.8 3.9 3.10
+  # Setup python and print version
+  setup-python:
+    needs: build-matrix
+    strategy:
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+      - run: python --version
+```
+
+## Inputs
+
+Inputs are the same as for the built-in matrix, but their syntax is slightly
+different.
+
+All inputs are optional with empty strings as default, but at least one of the
+three inputs must be specified.
+
+Only strings are allowed as GitHub action inputs, but you can use any
+whitespaces including newlines for word separation in all inputs. It is
+recommended to use (any) YAML multiline strings to unclutter your inputs, e.g.:
+
+```yaml
+with:
+  matrix: |
+    node-version: 12 14 16
+  include: |
+    node-version: 16
+    npm: 6
+```
+
+All words themselves must not contain any whitespaces, colons and commas. All
+other characters are allowed, but valid behaviour can not be validated for all
+possible characters, so be aware that both input parsing and later matrix usage
+could be affected by some edge cases.
+
+### `matrix`
+
+Optional base matrix configuration with the following syntax:
+
+```
+variable-1: value value <...>,
+variable-2: value value <...>,
+            <...>
+variable-n: value value <...>[,]
+```
+
+Variable names must be unique and differ from exact 'include' and 'exclude'
+strings reserved by the built-in matrix.
+
+### `include`
+
+Optioal extra matrix configurations to add to the base matrix. Must have the following
+syntax:
+
+```
+variable-i: value variable-j: value <...>,
+                   <...>
+variable-k: value variable-l: value <...>[,]
+```
+
+Variable names in each "row" should be unique but can differ from the ones in
+the [`matrix`](#matrix) input.
+
+### `exclude`
+
+Optional matrix configurations to exclude from the base matrix. Have the same syntax and
+restrictions as [`include`](#include).
+
+## Outputs
+
+Parsed matrix is printed inside the action's step as a pretty formated YAML
+using `yq`, so you can visually inspect it.
+
+Parsed matrix is also set as `MATRIX` environment variable.
+
+### `matrix`
+
+valid JSON matrix ready to be set as `jobs.<job_id>.outputs` used in
+`jobs.<job_id>.strategy`:
+
+```yaml
+matrix: ${{ fromJson(needs.<job_id>.outputs.matrix) }}
+```
+
+## Errors
+
+Not only syntax validity, but also built-in matrix' restrictions are checked. If
+you find a case where either of the checks does not work, feel free to report as
+an issue.
+
+Error logs try to give as much infomation on problem as possible.
+
+## Advanced usage
+
+### Reuse a matrix
+
+Sometimes you need to run different jobs os the same set of configurations, e.g.
+install python dependencies, check code quality and run unit tests.
+
+<details>
+    <summary>Solution using the built-in matrix</summary>
+
+```yaml
+jobs:
+  # No matrix build
+  # Setup python environment and cache installed packages
+  setup-python:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ['3.8', '3.9', '3.10']
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: python -m pip install -r requirements.txt
+  # Check code quality
+  check-code:
+    needs: setup-python
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ['3.8', '3.9', '3.10']
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: python -m pip install -r requirements.txt
+      - run: black --check .
+      - run: pylint .
+  # Test code
+  unit-test:
+    needs: setup-python
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ['3.8', '3.9', '3.10']
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: pytest
+```
+
+</details>
+
+```yaml
+jobs:
+  # Build matrix
+  build-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.build.outputs.matrix }}
+    steps:
+      - id: build
+        uses: druzsan/build-matrix@v1
+        with:
+          matrix: |
+            os: ubuntu-latest windows-latest macos-latest,
+            python-version: 3.8 3.9 3.10
+  # Setup python environment and cache installed packages
+  setup-python:
+    needs: build-matrix
+    strategy:
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: python -m pip install -r requirements.txt
+  # Check code quality
+  check-code:
+    needs: [build-matrix, setup-python]
+    strategy:
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: python -m pip install -r requirements.txt
+      - run: black --check .
+      - run: pylint .
+  # Test code
+  unit-test:
+    needs: [build-matrix, setup-python]
+    strategy:
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+          cache: pip
+      - run: python -m pip install -r requirements.txt
+      - run: pytest
+```
+
+### Build dynamic matrix
+
+Sometimes you need to run a job on different sets of configurations, depending
+on branch, triggering event etc.
+
+<details>
+    <summary>Solution using the built-in matrix</summary>
+
+```yaml
+jobs:
+  # No matrix build
+  # Test code on a dev branch
+  unit-test-dev:
+    if: github.ref != 'refs/heads/main' && !startsWith(github.ref, 'refs/tags/v')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '3.8'
+      - run: python -m pip install -r requirements.txt
+      - run: pytest
+  # Test code on the main branch
+  unit-test-main:
+    if: github.ref == 'refs/heads/main'
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        python-version: ['3.8', '3.9', '3.10']
+        include:
+          - os: windows-latest
+            python-version: 3.8
+          - os: macos-latest
+            python-version: 3.8
+    runs-on:
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+      - run: python -m pip install -r requirements.txt
+      - run: pytest
+  # Test code on a tag
+  unit-test-tag:
+    if: startsWith(github.ref, 'refs/tags/v')
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        python-version: ['3.8', '3.9', '3.10']
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:include:
+          python-version: '${{ matrix.python-version }}'
+      - run: python -m pip install -r requirements.txt
+      - run: pytest
+```
+
+</details>
+
+```yaml
+jobs:
+  # Build matrix
+  build-matrix:
+    runs-on: ubuntu-latest
+    steps:
+      - if: startsWith(github.ref, 'refs/tags/v')
+        uses: druzsan/build-matrix@v1
+        with:
+          os: ubuntu-latest windows-latest macos-latest
+          python-version: 3.8 3.9 3.10
+      - if: github.ref == 'refs/heads/main'
+        uses: druzsan/build-matrix@v1
+        with:
+          os: ubuntu-latest
+          python-version: 3.8 3.9 3.10
+          include: |
+            os: windows-latest python-version: 3.8,
+            os: macos-latest python-version: 3.8
+      - if: github.ref != 'refs/heads/main' && !startsWith(github.ref, 'refs/tags/v')
+        uses: druzsan/build-matrix@v1
+        with:
+          os: ubuntu-latest
+          python-version: 3.8
+      # MATRIX environment variable is set by the last executed action
+      - id: set-matrix
+        run: echo "matrix=$MATRIX" >> $GITHUB_OUTPUT
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+  # Test code
+  unit-test:
+    needs: build-matrix
+    strategy:
+      matrix: ${{ fromJson(needs.build-matrix.outputs.matrix) }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '${{ matrix.python-version }}'
+      - run: python -m pip install -r requirements.txt
+      - run: pytest
+```
+
+## Examples
+
+## Discussions
diff --git a/action.yml b/action.yml
index c76d2a5..6c2cf2a 100644
--- a/action.yml
+++ b/action.yml
@@ -1,12 +1,19 @@
 name: Build Matrix
 author: Alexander Druz
-description: GitHub action to create a reusable and potentially dynamic matrix for workflow jobs.
+description: Create reusable dynamic job matrices for your workflows.
 branding:
   icon: layers
   color: gray-dark
 inputs:
   matrix:
-    description: '...'
+    default: ''
+    description: Base matrix
+  include:
+    default: ''
+    description: Extra matrix combinations to include
+  exclude:
+    default: ''
+    description: Matrix combinations to exclude from matrix
 outputs:
   matrix:
     description: matrix in JSON format
@@ -17,5 +24,8 @@ runs:
     - name: Set matrix
       id: set-matrix
       run: |
-        echo "${{ inputs.matrix }}"
+        MATRIX="$(dist/parse-matrix.sh "${{ inputs.matrix }}" "${{ inputs.include }}" "${{ inputs.exclude }}")"
+        echo "$MATRIX" | yq -P '{"matrix":.}'
+        echo "MATRIX=$MATRIX" >> $GITHUB_ENV
+        echo "matrix=$MATRIX" >> $GITHUB_OUTPUT
       shell: bash
diff --git a/dist/parse-matrix.sh b/dist/parse-matrix.sh
new file mode 100755
index 0000000..b6574f0
--- /dev/null
+++ b/dist/parse-matrix.sh
@@ -0,0 +1,115 @@
+#!/bin/bash
+set -e
+
+HELP="Usage: $0 MATRIX INCLUDE EXCLUDE
+
+Parse a matrix for GitHub jobs in JSON format from the given arguments.
+
+MATRIX arguments should fulfill the following pattern with unique variable names different from the reserved 'include' and 'exclude':
+	variable-1: value value ...,
+	variable-2: value value ...,
+	             ...
+	variable-n: value value ...[,]
+INCLUDE and EXCLUDE arguments should fulfill the following pattern with unique variable names inside each combination:
+	variable-i: value variable-j: value ...,
+	                   ...
+	variable-k: value variable-l: value ...[,]
+All names and values of variables must not contain any spaces, colons and commas. Any spaces can be used for word and line separation."
+
+function fail {
+	# Print error message if given, print help and exit with code 1.
+	echo "Error${1:+: $1}" >&2
+	echo >&2
+	echo "$HELP" >&2
+	exit 1
+}
+
+function sanitize {
+	# Sanitize string as expected in further steps:
+	# - replace all spaces (including newlines) with simple whitespaces;
+	# - remove trailing comma if exists;
+	# - replace all other commas with newlines (i.e. split string by commas).
+	if [[ "$#" -ne 1 ]]; then
+		echo "Error: Single argument to sanitize expected, but $# arguments received." >&2
+		exit 1
+	fi
+	echo "${1//[[:space:]]/ }" | sed 's/,\s*$//g' | sed 's/,/\n/g'
+}
+
+if [[ "$#" -ne 3 ]]; then
+	fail "Exactly 3 arguments expected, but $# arguments received."
+fi
+
+INPUT_MATRIX="$1"
+declare -A INPUT_EXTRAS=([include]="$2" [exclude]="$3")
+MATRIX=""
+
+# Define REGEX patterns for grep.
+RE_WORD='[^\s:,]+'
+RE_VARIABLE="${RE_WORD}\s*:(\s*${RE_WORD})+"
+RE_COMBINATION="(${RE_WORD}\s*:\s*${RE_WORD}\s*)+"
+
+# Check if the whole matrix consists not only of spaces.
+if [[ -n "${INPUT_MATRIX//[[:space:]]/}" ]]; then
+	INPUT_MATRIX="$(sanitize "$INPUT_MATRIX")"
+	# Check if every row filfills the expected pattern.
+	if echo "$INPUT_MATRIX" | grep -qvP "^\s*${RE_VARIABLE}\s*$"; then
+		ERROR_MESSAGE="$(
+			echo "Invalid matrix rows found:"
+			echo "$INPUT_MATRIX" | grep -vP "^\s*${RE_VARIABLE}\s*$" |
+				sed 's/^\s*\|\s*$/\t/g;'
+		)"
+		fail "$ERROR_MESSAGE"
+	fi
+	VARIABLES="$(echo "$INPUT_MATRIX" | grep -oP "$RE_VARIABLE" |
+		jq -R 'capture("^\\s*(?<key>[^\\s:,]+)\\s*:(?<value>.*)$") | .value |= [scan("[^\\s:,]+")] | [.] | from_entries')"
+	# Check for duplicates in variable names.
+	DUPLICATES="$(echo "$VARIABLES" | jq 'keys' |
+		jq -rs 'add | group_by(.) | map(select(length>1) | .[0]) | join(", ")')"
+	if [[ -n "$DUPLICATES" ]]; then
+		fail "Following duplicated variable names found in matrix: ${DUPLICATES}."
+	fi
+	# Check for invalid variable names.
+	RESERVED_NAMES="$(echo "$VARIABLES" | jq 'keys' |
+		jq -rs 'add | map(select(test("^(include|exclude)$"))) | join(", ")')"
+	if [[ -n "$RESERVED_NAMES" ]]; then
+		fail "Following reserved variable names found in matrix: ${RESERVED_NAMES}."
+	fi
+	MATRIX="$(echo "${MATRIX}${VARIABLES}" | jq -s 'add')"
+fi
+
+for EXTRA_NAME in "${!INPUT_EXTRAS[@]}"; do
+	INPUT_EXTRA="${INPUT_EXTRAS[$EXTRA_NAME]}"
+	# Check if extra consists not only of spaces.
+	if [[ -n "${INPUT_EXTRA//[[:space:]]/}" ]]; then
+		INPUT_EXTRA="$(sanitize "$INPUT_EXTRA")"
+
+		# Check if every combination fulfills the expected pattern.
+		if echo "$INPUT_EXTRA" | grep -qvP "^\s*${RE_COMBINATION}\s*$"; then
+			ERROR_MESSAGE="$(
+				echo "Invalid combinations found in ${EXTRA_NAME}:"
+				echo "$INPUT_EXTRA" | grep -vP "^\s*${RE_COMBINATION}\s*$" |
+					sed 's/^\s*\|\s*$/\t/g;'
+			)"
+			fail "$ERROR_MESSAGE"
+		fi
+		EXTRA="$(echo "$INPUT_EXTRA" | grep -oP "$RE_COMBINATION" |
+			jq -R '[capture("(?<key>[^\\s:,]+)\\s*:\\s*(?<value>[^\\s:,]+)"; "g")]')"
+		DUPLICATES="$(echo "$EXTRA" | jq 'group_by(.key) | map(select(length>1) | .[0].key)')"
+		if [[ "$(echo "$DUPLICATES" | jq -s 'map(length) | add')" -ne 0 ]]; then
+			ERROR_MESSAGE="$(
+				echo "Duplicated variable names found in ${EXTRA_NAME}:"
+				echo "$DUPLICATES" | jq -rs 'map(join(", ")) | to_entries | map(select(.value != "")) | map("Combination " + (.key | tostring) + ": " + .value) | .[]'
+			)"
+			fail "$ERROR_MESSAGE"
+		fi
+		EXTRA="$(echo "$EXTRA" | jq 'from_entries' | jq -s "{$EXTRA_NAME: .}")"
+		MATRIX="$(echo "${MATRIX}${EXTRA}" | jq -s 'add')"
+	fi
+done
+
+if [[ -z "$MATRIX" ]]; then
+	fail "At least one of matrix, include or exclude should be not empty"
+fi
+
+echo "$MATRIX" | jq -c