This code is neither robust nor efficient nor general. But it's short and fun.
Making it any of those things is not difficult, but it won't be
do-able in 56 chars.
It doesn't deal with escaped or quoted parens -- i.e. they are
treated like any other. It doesn't deal with nulls in the input very well, to make it do that would cost 3 extra chars.
It doesn't let you know where you're unbalanced, but simply prints `1' if
the input is balanced and prints nothing if it's not.
Oh, and it requires 5.6.0 or better.
Give it a filename to check for balancing on the command line, or
run it as shown below exactly and give it text to check on standard input.