The following code passes your tests. It uses a single if and a hash ref as a "poor man's switch":

for (@test) {
    if (/ .* (^|\() (.*?) (\)|$) /x and my $p = "$1$3") {
        print ' Match ',
            { ')'  => 'before right paren',
              '('  => 'after left paren',
              '()' => 'in parens',
            }->{$p},
            ": $2\n";
    }
}
[download]

It's not clear, though, what should happen if the parentheses were nested.