use strict;
use warnings;
my $label1 = 'L1';
my $label2 = 'L2';
my %hash;
@hash{'a' .. 'h'} = (
    {$label1 => 1 },
    {$label1 => 2 },
    {$label2 => 3 },
    {$label1 => 4 },
    {$label2 => 5 },
    {$label1 => 6 },
    {$label2 => 7 },
    {$label1 => 8 },
);
while ( my( $key,$subhash ) = each %hash) {
    print "$key: $subhash->{$label1}\n" if exists $subhash->{$label1};
}