This might be a silly question but is it more efficient to declare and uses hashes that way (reference)
No, a direct hash will be marginally faster.

PS this is wrong: 

my %student = {};

[download]
it should be 
my %student = ();

[download]
or even just 
my %student;

[download]
as the hash is created empty already

Dave.

In reply to Re: Hashes and hash references by dave_the_m
in thread Hashes and hash references by Anonymous Monk

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