hmmm...code produced a syntax error for me on the while line.

@foo = ('a(b(c)d(e(f)g)h)i(j(k)l(m)n)o',
        'a(b(c)d(e(f)g)h)i(j(k)l(m)n)o)');

for (@foo) {
   print "\'$_\' has ";

   while ( s/\([^()]*\)// ){}

   print "un" if /[()]/;
   print "balanced parentheses\n";
}
[download]

Just a few minor modifications.

While you can use an algorithm like this to find if a string has matches parens, you can't write a single regexp that does it. Check out this node for a bit of an explination for this.

/\/\averick