如何从数组中减去数组？

Question

当我尝试以下

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my @bl = qw(red green blue);
my @a = qw(green yellow purple blue pink);

print Dumper [grep {not @bl} @a];

我得到一个空数组.我原以为会@bl减去@a,所以输出是yellow purple pink.

这有什么不对？

Answer 1

您需要@bl变成哈希来执行设置差异:

my %in_bl = map {$_ => 1} @bl;
my @diff  = grep {not $in_bl{$_}} @a;