but $hashVar is global. Why should HashClean recreate it? If you want a new instance of $hashVar every time you enter HashClean then $hashVar needs to be local to HashClean.

It seems that what you are trying to do is recursively traverse a mixed hash and array structure and clean it up. Maybe the following will help:

use strict;
use warnings;

sub clean {
    my $ref = shift;
    
    if ('HASH' eq ref $ref) {
        clean ($ref->{$_}), $ref->{$_} = undef for keys %$ref;
    } elsif ('ARRAY' eq ref $ref) {
        clean ($_), $_ = undef for @$ref;
    }
}


my $hashvar = {
    emp => {},
    hemp =>
        {splay => {}, hay => {go => 1, ho => {},}, tay => [], may => [
+'way'],},
        };

clean ($hashvar);
$hashvar = undef;
[download]

Update: rereading the OP I see that deleting the whole structure is not quite what you want, but the code above should still be a good starting point for getting to where you want to go. In fact the following may just do the trick:

use strict;
use warnings;
use Data::Dump::Streamer;

sub clean {
    my $ref = $_[0];
    
    if ('HASH' eq ref $ref) {
        clean ($ref->{$_}) and delete $ref->{$_} for keys %$ref;
        return ! keys %$ref;
    } elsif ('ARRAY' eq ref $ref) {
        clean ($ref->[$_]) and delete $ref->[$_] for reverse 0 .. $#$r
+ef;
        return ! @$ref;
    } else {
        return ! defined $ref;
    }
}


my $hashvar = {
    emp => {},
    hemp =>
        {splay => {}, hay => {go => 1, ho => {},}, tay => [], may => [
+'way'],},
        };

clean ($hashvar);
Dump ($hashvar);
[download]

prints:

$HASH1 = { hemp => {
           hay => { go => 1 },
           may => [ 'way' ]
         } };
[download]

Tip for the future - show what you expect as well as what you get.