I suspect it's because $h{HELP} doesn't exist when you create the tuple Q=>$h{HELP}, as %h hasn't been assigned to at that time.

Perhaps this will work for you:

use Data::Dumper;
my %h=(   HELP => sub {print qq(help\n)},

                SAVE=>sub{print qq(save\n)} ); 
$h{Q} = $h{HELP};
print Dumper(%h);
print $h{Q}();
[download]

Result:

$VAR1 = 'Q';
$VAR2 = sub { "DUMMY" };
$VAR3 = 'HELP';
$VAR4 = $VAR2;
$VAR5 = 'SAVE';
$VAR6 = sub { "DUMMY" };
help
1
[download]

Note that HELP and Q both use the same sub.

-QM
--
Quantum Mechanics: The dreams stuff is made of