Question

I load the following YAML stream into a Perl’s array and I want to traverse the array associated with Field2.

use YAML;

my @arr = Load(<<'...');
---
Field1: F1
Field2:
 - {Key: v1, Val: v2}
 - {Key: v3, Val: v4}
---
Field1: F2
Field2:
 - {Key: v5, Val: v6}
 - {Key: v7, Val: v8}
...

foreach (@arr) {
    @tmp = $_->{'Field2'};   
    print $#tmp; # why it says 0 when I have 2 elements?

    # Also why does the below loop not work? 
    foreach ($_->{'Field2'}) {
    print $_->{'Key'} . " -> " $_->{'Val'} . "\n";
 }
}

I appreciate any feedback. Thank you.

Answer 1

Because you are not using references correctly. You may want to reread perldoc perlreftut and perldoc perlref.

#!/usr/bin/perl

use strict;
use warnings;

use YAML;

my @arr = Load(<<'...');
---
Field1: F1
Field2:
 - {Key: v1, Val: v2}
 - {Key: v3, Val: v4}
---
Field1: F2
Field2:
 - {Key: v5, Val: v6}
 - {Key: v7, Val: v8}
...

for my $record (@arr) {
     print "$record->{Field1}:\n";
     for my $subrecord (@{$record->{Field2}}) {
         print "\t$subrecord->{Key} = $subrecord->{Val}\n";
     }
}