How to recognize a phone number in SMS content and reply an SMS to that number?

MagiCall 2.1 introduced a new contextual parameter: {keyword}, which can be used to receive the first matched keyword in SMS content.
How to use it? Please take a look at the following example:

Rule type: SMS
Filter type: All
SMS filter: <\d{8,}>
Action2: Send SMS
To: {keyword}
Message: Blah, blah, blah

In the rule above, we use the regular expression "\d{8,}" to find strings consisting of 8 or more digits, and then send an SMS to the first found string.
That says, for example, when you receive an SMS with this content: "Please send an SMS to me at 987654321", the rule above will send an SMS to 987654321.

Further more, you may also use regular expressions to find email addresses in SMS content, and send an email to them.