You may find changing $j to $hr so you know it's a hashref makes things a bit clearer.

#!perl
use strict; 
use Data::Dumper;

my %hash = ( key => 12, pl  => 1, lop => 9 );
my %hash2 = ( key => 12, pl  => 1, lo => 9 );

my @arr = ( [\%hash,\%hash2] );

for my $i (0 .. $#arr){
    my $subd = @{$arr[$i]};
    print "subLen: $subd\n";
    for my $hr (@{$arr[$i]}){
      for my $key (keys %$hr){
        print $key.": ".$hr->{$key}."\n";
      }
    }
}
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