No, like:

for my $n (@nra) {
    my $fmt;
    if ($n > 0.001){
        $fmt = '%5.2g';  
        }
    else {
        $fmt = '%5.3g';
        }
    printf qq{$fmt \n}, $n;
    }
[download]

See Conditional Operator in perlop.

Note that
    $x = $y > $z ? 'foo' : 'bar';
is perhaps more clearly written as
    $x = ($y > $z) ? 'foo' : 'bar';