Hi try this,

#!/usr/local/bin/perl

use strict;
use warnings;
use Data::Dumper;

my %commands =  (
   'command1'  => {
      'description' => "Does something",
      'function'    => sub { my $var = shift; return "var = $var\n" }
        }
 );

my $cmd = 'command1';
print $commands{$cmd}{'function'}->("hello");
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It's reference part, to learn more about reference, go through perlref link, above given by duff.