You need to populate the hash with code-references (\&sub).

Try: 

use strict;

# my $code_ref = {'SUM', 'sum'};  
  my $code_ref = {'SUM', \&sum};

sub sum($$){...}   # do you really need ($$) ? That is rarely useful. 

# ($codes->{'SUM'})->(4,5);   # $codes? You mean $code_ref?
$code_ref->{'SUM'}->(4,5);

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In reply to Re: HASH value as a subroutine call by Perlbotics
in thread HASH value as a subroutine call by enigma

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