Maybe it's time consider refactoring this via CPAN modules? For comparison, the following achieves a similar result, using File::Find::Rule and Filesys::DiskUsage:

#/usr/bin/perl
use warnings; use strict;

use Filesys::DiskUsage qw/du/;
use File::Find::Rule;
use YAML;

my $rule = File::Find::Rule->new;
$rule->directory();
$rule->not($rule->new->name( qr/^.*Maildir.*(cur|new|courierimapkeywor
+ds)$/));
my @dirs = $rule->in('.');
warn "dirs=@dirs";

my %sizes = du( {
         'make-hash' => 1,
         'human-readble' => 1,
        } ,  @dirs);
 
print YAML::Dump(\%sizes);
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