Question

My hash looks like this :

$VAR1 = {
      '1238' => {
                  'OUT3FA_5' => 65,
                  'SEV' => '3_major',
                  'OUT3A_5' => 20,
                  'OUT3-Fix' => 45,
                  'IN1' => 85
                },
      '1226' => {
                  'OUT3FA_5' => 30,
                  'SEV' => '4_minor',
                  'OUT3A_5' => 5,
                  'OUT3-Fix' => 25,
                  'IN1' => 40
                },
      '1239' => {
                  'OUT3FA_5' => 56,
                  'SEV' => '4_minor',
                  'OUT3A_5' => 34,
                  'OUT3-Fix' => 22,
                  'IN1' => 94
                }]

I want my Perl script to only return the values corresponding to “SEV” = “4_minor” In this case it’ll return :

    '1226' => {
                  'OUT3FA_5' => 30,
                  'SEV' => '4_minor',
                  'OUT3A_5' => 5,
                  'OUT3-Fix' => 25,
                  'IN1' => 40
                },
      '1239' => {
                  'OUT3FA_5' => 56,
                  'SEV' => '4_minor',
                  'OUT3A_5' => 34,
                  'OUT3-Fix' => 22,
                  'IN1' => 94
                }

But when I use grep like this :

my $Sev_Logged = "4_minor";
my $node_hash = {
Week => [
  grep {  $hash{$_}{'SEV'} eq $Sev_Logged } %hash,
   ]
    };

# Print in json format
my $json = encode_json \%$node_hash;
print $json;

It only returns :

{"Week":["1226","1239"]}

And I want it to return all the other data corresponding to each of the weeks found containing SEV=”4_minor”.
How can I do this?
Any help would be much appreciated.

Answer 1

When you hand a %hash over that way to grep then Perl interpretes the hash as an even-numbered list of keys and values — resulting in the grep {...} block being called for once for each key and once for each value (instead of being called for each pair of key&value).

Try something like this:

{ map { ($_ => $hash{$_} } grep { $hash{$_}->{SEV} eq $Sev_Logged } keys %hash }

The grep keeps those hash keys for which the SEV field matches what you want. The map afterwards reconstructs a hash (because at that moment we only have the keys returned from grep), and finally we convert it to a hash reference.