ABAP: Use if-condition in string template

My Problem is to integrate an if-statement into a string template.

mt_fields = VALUE #(
    ( name = 'HI'      label = 'Greeting' )
    ( name = 'PERSON'  label = 'Who' )
    ( name = 'RESULT'  label = 'Sentence'  result = |Say \{HI\} to \{PERSON\}.| )
)

(That kind of construction does not make much sense, it's just for an MWE.)

What I want to get: Some times there is no data for PERSON. In that case, the result variable will get the string 'Say hello to .' (if 'hello' is the value for HI).

I dont want to have this. If there is no person, I want to get an empty string as result. So I have to filter first, whether there is some value for PERSON or not. I need to get an if-condition into the string assignment.

In Python I would write something like

( name = 'RESULT'  label = 'Sentence'  result = 'Say {HI} to {PERSON}.' IF PERSON != '' ELSE '' )

But how to do this in ABAP?

Thanks a lot!