sub is_balanced { eval "qw($_[0])" }

##</code><code>##

$ perl -le'
sub is_balanced { eval qq($_[0]) }

my $balanced   = "(1 + 2 * (3 + (5/4) + 8) + 6)";
my $unbalanced1 = "(((1 + 2 * (3 + (5/4) + 8) + 6))";
my $unbalanced2 = "(((1 + 2 * (3 + (5/4) + 8) + 6))))";

print "Is $balanced balanced? ", is_balanced( $balanced ) ? "yes" : "no";
print "Is $unbalanced1 balanced? ", is_balanced( $unbalanced1 ) ? "yes" : "no";
print "Is $unbalanced2 balanced? ", is_balanced( $unbalanced2 ) ? "yes" : "no";
'
Is (1 + 2 * (3 + (5/4) + 8) + 6) balanced? yes
Is (((1 + 2 * (3 + (5/4) + 8) + 6)) balanced? no
Is (((1 + 2 * (3 + (5/4) + 8) + 6)))) balanced? no