use strict;
use warnings;
use Data::Dumper;

my %chrHash;

push @{ $chrHash{"chr1"}{3} }, 100;
push @{ $chrHash{"chr1"}{3} }, 300;

print 'Count for chr1 3: ', scalar @{ $chrHash{"chr1"}{3} }, "\n";
print qq/Locations for chr1 3: @{ $chrHash{"chr1"}{3} }\n\n/;

print Dumper \%chrHash;