I prefer to never initialize a variable as empty. Why? It is the best way to find out if you are actually using the variable in your code. Quick sample,

use warnings;
my $retval = 0;

warn "Return Value $retval\n";
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You have not done anything with this value, and nothing gets reported as being a problem. If you do this,

use warnings;
my $retval;

warn "Return Value $retval\n";
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You are going to get an uninitialized value warning, you will probably be saying WTF? Until you look and realize the code that you wanted was this,

use warnings;
my $retval;

$retval = get_value_from_subroutine();

warn "Return Value $retval\n";
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It also reduces the amount of code that you have, I admit it is small, but do it a couple of hundred times, you get the idea.