Pulling Array Out of Hash Reference

enoch has asked for the wisdom of the Perl Monks concerning the following question:

If I have a reference to a hash, is there anyway to index into the referenced hash via an array and pull out those values that correspond as keys in the array. I know... I know... that was a complex sentence. In code:

my %hash = (
             a => 'foo',
             b => 'bar',
             c => 'baz',
             d => 'quux',
           );

print @hash{'a','d'},"\n"; # correctly prints out "fooquux"

my $hashRef = \%hash;

# generates error
# "Not an ARRAY reference at hashArrayPlay.pl line 16."
print @$hashRef->{'a','d'};
[download]

I have tried various iterations trying to get it to reference correctly. And, I have read through perldata and perlref trying to find an answer to this. Does anyone have any insight?

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Re: Pulling Array Out of Hash Reference by enoch (Chaplain) on Apr 12, 2004 at 22:44 UTC
"`Hash slice`." That was the term I was looking for, which immediately took me to "How do I take a slice of a hash reference?," which answered my question.	[reply] [d/l]
Re: Pulling Array Out of Hash Reference by kvale (Monsignor) on Apr 12, 2004 at 22:43 UTC
You are very close: `print @{ $hashRef->{'a','d'} };` [download] To satisfy operator precedence, the braces are needed in the array dereference. -Mark	[reply] [d/l]
Re: Re: Pulling Array Out of Hash Reference by antirice (Priest) on Apr 12, 2004 at 23:05 UTC
I believe you meant: `print @{ $hashRef }{'a','d'};` [download] Your code attempts to deref `$hashRef->{join $;,'a','d'}` which is undefined. antirice The first rule of Perl club is - use Perl The ith rule of Perl club is - follow rule i - 1 for i > 1	[reply] [d/l] [select]
Re^3: Pulling Array Out of Hash Reference by tye (Sage) on Apr 12, 2004 at 23:24 UTC
Which can also be written as `print @$hashRef{'a','d'};` [download] as outlined in references quick reference (which is how I finally figured out that all of this syntax is pretty easy to keep straight). But I think I'd stick with `print @{$hashRef}{'a','d'};` [download] as being clearer. - tye	[reply] [d/l] [select]
Re: Re^3: Pulling Array Out of Hash Reference by antirice (Priest) on Apr 13, 2004 at 00:13 UTC
Re: Re: Re: Pulling Array Out of Hash Reference by kvale (Monsignor) on Apr 12, 2004 at 23:22 UTC
Blush, a bad test on my part. You are entirely correct. -Mark	[reply]


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