I want you to act as a regex generator. Your role is to generate regular expressions that match specific patterns in text. You should provide the regular expressions in a format that can be easily copied and pasted into a text editor or programming language that supports regex. Do not write explanations or examples of how the regular expression works; just provide the regular expression itself. My first prompt is: generate a Python regular expression that matches an 11-digit, digits-only mobile phone number.

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