%mapp = ();
@arr = ("R", "T", "HH", "M");
$mapp{"FirstKey"} = \@arr;
@val = $mapp{"FirstKey"};
print join (",", @{$mapp{"FirstKey"}}) . "\n";   #The array will be printed 
push(@val, "RBB");
$mapp{"FirstKey"} = \@val;
print join (",", @{$mapp{"FirstKey"}}) . "\n";  #an array reference will be printed

##</code><code>##

R,T,HH,M
ARRAY(0x7ffafc013bf8),RBB