Hello AhmedABdo,

There are many many ways on solving your problem, one way could be:

I would recommend to read the List::Compare module.

Be aware in your example that you provided us, the values of the hash is and nice are not one string as in the array so as expected they will not match.

Update: please every time you update your question / reply provide and update so can follow. You have altered your question and my reply is not suitable to you any more. I will post another reply in a few hours when I will get back to my pc.

Update2: An alternative solution to your problem:

Update3: In case you want your keys sorted:

Update4: Maybe this solution is faster using grep:

Update5: Maybe map is fast I am not sure though:

Update6: Maybe smartmatch is fast I am not sure though, but it has been placed as experimental see (The smartmatch family of features are now experimental):

Update7: I could not resist I benchmark them and here is what I found:

Please on your next question that you will post on the forum follow the guided lines (How do I post a question effectively?).

Hope this helps.

I would use reverse for this:

my @array = qw(world today is very nice);
my %hash = (0 => "Hello", 1=> "world" , 2=> "today" , 3=> "is" , 4=> "
+nice" );

my %reversed_hash = reverse %hash;
foreach my $word ( @array )
{
    if ( exists $reversed_hash{ $word } )
    {
        print $reversed_hash{ $word } . "\n";
    }
    else
    {
        print "unknown '$word'\n";
    }
}
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Output:

1
2
3
unknown 'very'
4
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I tried to use lookup with loop thought the array but it did not work.

Could you show us the code you tried? The approaches you describe should work, so perhaps we can help you fix the issues with your code. See How do I post a question effectively?

Also, are all the values in the hash unique? If so, you could simply build an inverse hash using reverse and use that for lookups.

G'day AhmedABdo,

This looks like an "XY Problem" to me. In addition, it looks like you've typed, rather than pasted, your code, which has resulted in typos: My should be my; "Hello" is either missing from @array, extraneous to %hash, or an explanation of how it relates to the rest of your post has been omitted. I see others have already pointed out further issues: I won't repeat those comments here but I do agree with them.

Perhaps what you're looking for can be achieved with the enum module. Here's a script with a couple of examples of usage:

#!/usr/bin/env perl -l

use strict;
use warnings;

use enum qw{world=1 today is nice};

print '"world today" from enum';
print for world, today;

print '"today is nice" from array';
my @indices = (today, is, nice);
print for @indices;
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Output:

"world today" from enum
1
2
"today is nice" from array
2
3
4
[download]

Hello kcott,

In this case enum fits perfect. Thanks for pointing out, I had no idea about it.

Seeking for Perl wisdom...on the process of learning...not there...yet!

Glad you liked it.

Here's another, more complex example of usage, that I posted last month. This shows a method of determining the original token name from the index.

— Ken

See the FAQ.

I tried to use lookup with loop thought the array but it did not work.

"It did not work" is as useful to a developer as "I'm ill" is to a medic. Try to be specific.

AhmedABdo: The specific entry in the FAQ is "How do I look up a hash element by value?" in the "Data: Hashes (Associative Arrays)" section (it cannot be linked to directly for some reason). (Update: Per hippo, failure to link seems to be a "feature" of my browser, IE. Oh, well...)

---

Give a man a fish:  <%-{-{-{-<

While the proposed solution of reversing the hash is technically correct, I can't help but think that the real solution probably is to construct the hash correctly in the first place.

Going even further, your question looks like a XY Problem: you are asking about the way to correct an issue that you encountered while trying to solve a bigger problem.

So I strongly advise you to read How do I post a question effectively? And then post a description of your global problem, and how your array and hash are elements of your attempted solution.

Edit: Not_a_Number told me my second paragraph was confusing, so I rephrased and went straight to the point.

Please show your code, and the undesirable output it gave. You might be close !

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1185598

use strict;
use warnings;

my @array = qw(world today is very nice);
my %hash = (0 => "Hello", 1=> "world" , 2=> "today" , 3=> "is" , 4=> "
+nice",
  5=> "is");

my %reversehash; # allow for different keys mapping to the same value
push @{ $reversehash{$hash{$_}} }, $_ for keys %hash;

my @newarray = map @{ $reversehash{$_} // [] }, @array;

use Data::Dumper; print Dumper \@newarray;
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