数组求差集

oadb01:/home/oracle> cat a1.pl 
my @a=qw(1 2 3 4 5 aa bb );
my @b=qw(1 2 );
@b = grep {$count{$_} == 1 } grep {++$count{$_}} (@a, @b);
print "@b
"
oadb01:/home/oracle> perl a.1
Can't open perl script "a.1": No such file or directory
oadb01:/home/oracle> perl a1.pl 
3 4 5 aa bb