#! perl
use strict;
use warnings;

package Doohickey;
require Tie::Scalar;
our @ISA = 'Tie::StdScalar';

# returns the value you presumably want to print.
sub FETCH {
  "Hi\n";
}

# This actually prints a value, and then if you use the assignment,
# the FETCH is called that returns a value
sub STORE {
  my ($this, $val) = @_;
  print "I see arguments ($val)\n";
}

package main;

my $enemy;

tie $enemy->{strength}, 'Doohickey';

printf "%s\n", $enemy->{strength} = 5; # you could "pass" a ref to an argument list, too
print "...\n";
print $enemy->{strength}, "\n";