See

$ perl -MO=Deparse
$f= grep {/f/} @array ? 1 : 2;
<EOF>
$f = grep({/f/;} @array ? 1 : 2);
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Note that you have other options beside what you listed. I'd have chosen: $f= grep( /f/, @array ) ? 1 : 2;

You were on the right track as to the source of your problem with your node title (originally just "precedence"). To quote bits from "perldoc perlop":

    left        terms and list operators (leftward)
    [...]
    right       ?:
    [...]
    nonassoc    list operators (rightward)
[...]
Terms and List Operators (Leftward)

    A TERM has the highest precedence in Perl. They include 
    [...] any function whose arguments are parenthesized.
[...]
List Operators (Rightward)

    On the right side of a list operator, it has very low
    precedence, such that it controls all comma-separated
    expressions found there. The only operators with lower
    precedence are the logical operators "and", "or", and
    "not", which may be used to evaluate calls to list
    operators without the need for extra parentheses:

        open HANDLE, "filename"
            or die "Can't open: $!\n";
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which means that list operators bind tighter than ?: if you use parens but looser if you don't.

        - tye (but my friends call me "Tye")