diff --git a/chatmastermind/message.py b/chatmastermind/message.py
new file mode 100644
index 0000000..cb426e7
--- /dev/null
+++ b/chatmastermind/message.py
@@ -0,0 +1,52 @@
+"""
+Module implementing message related functions and classes.
+"""
+from typing import Type, TypeVar
+
+QuestionInst = TypeVar('QuestionInst', bound='Question')
+
+
+class MessageError(Exception):
+    pass
+
+
+def source_code(text: str, include_delims: bool = False) -> list[str]:
+    """
+    Extracts all source code sections from the given text, i. e. all lines
+    surrounded by lines tarting with '```'. If 'include_delims' is True,
+    the surrounding lines are included, otherwise they are omitted. The
+    result list contains every source code section as a single string.
+    The order in the list represents the order of the sections in the text.
+    """
+    code_sections: list[str] = []
+    code_lines: list[str] = []
+    in_code_block = False
+
+    for line in text.split('\n'):
+        if line.strip().startswith('```'):
+            if include_delims:
+                code_lines.append(line)
+            if in_code_block:
+                code_sections.append('\n'.join(code_lines) + '\n')
+                code_lines.clear()
+            in_code_block = not in_code_block
+        elif in_code_block:
+            code_lines.append(line)
+
+    return code_sections
+
+
+class Question(str):
+    """
+    A single question with a defined prefix.
+    """
+    prefix = '=== QUESTION ==='
+
+    def __new__(cls: Type[QuestionInst], string: str) -> QuestionInst:
+        """
+        Make sure the question string does not contain the prefix.
+        """
+        if cls.prefix in string:
+            raise MessageError(f"Question '{string}' contains the prefix '{cls.prefix}'")
+        instance = super().__new__(cls, string)
+        return instance