How to split user message after Aiogram Python command?

Question

Bots

Let's say there is a command !hello, where the bot greets a person. I want to make it possible to add any custom replica to the "hello" command. The user writes: !hello how are you. The bot splits the user's message, where it finds his message how are you , and then the bot responds like this: the user greeted the user with the words how are you,

in fact the task is simple, I roughly understand how to do it, but I'm still not sure, split method?
and yes, I just need an example of text splitting, a handler and a function I can write, thanks!