Run perl -MO=Deparse on your code to see what it looks like after optimization. On Perl 5.5.3 on my box, it doesn't change it.

As for a benchmark, here's what I used:

sub trinary {
    my $a = 1;
    my $b = 0;
    return $a > $b ? $a : $b;
}

sub if_else {
    my $a = 1;
    my $b = 0;
    if ($a > $b) {
        return $a;
    } else {
        return $b;
    }
}

use Benchmark;
timethese(500000, {
    trinary => \&trinary,
    if_else => \&if_else,
});
[download]

You can play with different ways of constructing the if-else block. With 500,000 iterations, the ternary is 4% faster. I wouldn't worry about a difference like that.

Removing the else flips it the other way:

sub if_else {
    my $a = 1;
    my $b = 0;
    return $a if $a > $b;
    return $b;
}
[download]