Can procmail intercept incoming messages to a mailing list and modify it before letting it be delivered to the mailboxes of the members of the ML?

I have an email address (a mailing list actually) with a basic procmail setup enabled. Right now, the procmail just dumps incoming emails to fs. I have a use-case where I want to add a custom string to be prepended to each email's body which is received this ML. I've been reading up on procmail for the past few days and all the answers/examples I see related to modifying email subjects/bodies either explicitly use sendmail to "forward" the modified email or dump the modified email it to a custom mailbox. What I want is to intercept the message before it is delivered to the ML, prepend some custom text to its body and then let it be delivered to the originally intended ML (i.e. mailboxes of the members of the ML). Is there a way to achieve this?