pattern matching of variant tag in OCaml

I have the following OCaml substitution function.

let rec subst x a f =                                                                                                                                    
    match f with                                                                                                                                           
    | Var s -> if s = x then a else Var s                                                                                                                 
    | Implies (f1, f2) -> Implies (subst x a f1, subst x a f2)                                                                                            
    | And (f1, f2) -> And (subst x a f1, subst x a f2)                                                                                                     
    | Or (f1, f2) -> Or (subst x a f1, subst x a f2)                                                                                                                                                                                   
    | True | False as e -> e

Some cases are almost identical and I'm wondering if there's a way to factorize them somehow.

Ideally, I'm thinking of a construct of the form:

match f with
| tag (f1, f2) -> tag (subst x a f1, subst x a f2)
| ... 

that would match all my binary operations.

An other use case would be in a to_string function where we could have:

match f with
| tag (f1, f2) -> print_string ((tag_to_string tag) ^ ...  )
| ... 

I know this isn't possible in OCaml, but is there a pattern or a language construct that goes in that direction?