my $a = 0;
my $b = 0;
my $c = 1;

print "true1\n" if $a and $b or $c;
print "true2\n" if $a and ($b or $c);
print "true3\n" if ($a and $b) or $c;
print "true4\n" if $a and $b || $c;
print "true5\n" if ($a and $b) || $c;