Check if pattern exists in a keys of hash

Question

I have a hash of following pattern

my %hash_table(
     23                => someintegertype,
     type              => somestringtype,
     12_someidentifier => someveryproblematictype
);

How do I check if pattern that 12_someidentifier key follows exists in the hash or not? If so, I need to know the value in the form of true or false.

::UPDATE:: I wanted to check if the regex or pattern such as {[\d]_[\w+]} exists or not?

You're missing an `=` sign. – reinierpost Oct 13 '15 at 15:03 — reinierpost, Oct 13 '15 at 15:03

Sobrique · Accepted Answer · 2015-10-13T12:03:29.533

1

exists tells you if a key exists. $hash{$key} gives you the value, so you can test it.

If you're looking to test multiple values against a regex (such as they keys of a hash) then the tool for the job is grep;

my @matches = grep { /\d+_\w+/ } keys %hash_table;
print @matches;

Whilst we're at it - turn on use strict; and use warnings;. It'll help in the long run.

edited Oct 13 '15 at 12:03

answered Oct 13 '15 at 11:57

Sobrique

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I have updated my question. – Recker Oct 13 '15 at 12:00
1

OK. You're looking for matches in your keys - the tool for the job is `grep`. – Sobrique Oct 13 '15 at 12:03

score 0 · Answer 2 · answered Oct 13 '15 at 11:57

0

You can check like this:

if (exists $hash_table{$12_someidentifier})
{
        print $12_someidentifier, "\n";
}

answered Oct 13 '15 at 11:57

serenesat

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I have updated my question. – Recker Oct 13 '15 at 12:00
Your pattern is the key, and in Perl above is the way to check key exists in a hash or not. – serenesat Oct 13 '15 at 12:03
The above solution will cause vivification. May not matter, but generally isn't a great idea when dealing with hashes. – Jeffrey Tackett May 14 '17 at 22:53

Check if pattern exists in a keys of hash

2 Answers2