WMA link
f @ x
f[x]
a @ b
a @ b @ c
Format[p[x_]] := Prefix[{x}, "*"]
p[3]
Format[q[x_]] := Prefix[{x}, "~", 350]
q[a+b]
q[a*b]
q[a]+b
The prefix operator @ is parsed to an expression before evaluation:
@
Hold[a @ b @ c @ d @ e @ f @ x]