my $hash_name = "platform_$site";
%$hash_name = ( key => $value );
:
my $value = ${$hash_name}{key};

##</code><code>##

my %global_hash;
my $hash_name = "platform_$site";
$global_hash{$hash_name} = { key => $value };
:
my $value = $global_hash{$hash_name}{key};