如何从Perl中的sub传递和返回哈希？

Question

我一直在玩Perl中的哈希.以下按预期工作:

use strict;
use warnings;

sub cat {
        my $statsRef = shift;
        my %stats = %$statsRef;

        print $stats{"dd"};
        $stats{"dd"} = "DDD\n";
        print $stats{"dd"};
        return ("dd",%stats);
}

my %test;
$test{"dd"} = "OMG OMG\n";

my ($testStr,%output) = cat (\%test);
print $test{"dd"};

print "RETURN IS ".$output{"dd"} . " ORIG IS ". $test{"dd"};

输出是:

OMG OMG
DDD
OMG OMG
RETURN IS DDD
 ORIG IS OMG OMG

当我在混合中添加一个数组时,它会出错.

use strict;
use warnings;  sub cat {
        my $statsRef = shift;
        my %stats = %$statsRef;

        print $stats{"dd"};
        $stats{"dd"} = "DDD\n";
        print $stats{"dd"};         return ("dd",("AAA","AAA"),%stats); }
 my %test; $test{"dd"} = "OMG OMG\n";

my ($testStr,@testArr,%output) = cat (\%test);
print $test{"dd"};

print "RETURN IS ".$output{"dd"} . " ORIG IS ". $test{"dd"}. " TESTARR IS ". $testArr[0];

输出是:

OMG OMG
DDD
OMG OMG
Use of uninitialized value in concatenation (.) or string at omg.pl line 20.
RETURN IS  ORIG IS OMG OMG
 TESTARR IS AAA

为什么数组显示但哈希不是？

Answer 1

所有列表都在Perl中自动展平.因此,赋值运算符将无法神奇地区分子例程返回的列表之间的边界.在你的情况下,这意味着@testArr将使用由给定的结果列表cat,并且%输出将不会得到它 - 因此Use of unitialized value...警告.

如果需要专门返回散列或数组,请使用引用:

return ("dd", ["AAA", "AAA"], \%stats);

......以及之后的作业:

my ($testStr, $testArrayRef, $testHashRef) = cat(...);
my @testArray = @$testArrayRef;
my %testHash  = %$testHashRef;