Regular expression for strings with an even number of zeroes and ones

Question

What is a regular expression for strings of 0 and 1 with an even number of zeros and an even number of ones?

I have something like (1*01*01*)*(0*10*10*)*

Answer 1

@tmp = $str =~ /0/g;

print scalar @tmp % 2 == 0 ? 'even' : 'odd';