• perlref
• perlreftut
• References quick reference

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

my $emp_data = { "bob" => { salary => 38.7, # in k$/yr 
          sales => 23, # units 
      }, "jane" => { salary => 50.3, sales => 36, } };

my $bref = comp($emp_data);
print Dumper($bref);

sub comp {
    my $data = shift;
    my %bonus;
    for my $e (keys %{ $data }) {
        if ($data->{$e}{sales} > 30) {
            my $b = 0.20 * $data->{$e}{salary};
            $bonus{$e} = $b;
        }
    }
    return \%bonus;
}

__END__

$VAR1 = {
          'jane' => '10.06'
        };
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