#!/usr/bin/perl

use warnings;
use strict;

use File::Find;
use File::Spec::Functions;

my $directory = 'foodir';
my $size = 0;
my @unreadables = ();
my @errors = ();

sub wanted {
    # test: handling of @errors
    #local $_ = $_;
    #if (/foo\.txt/) {
    #    $_ = "nonexistentfile";
    #}
    
    if (stat) {
        -f _ and $size += -s _;
    }
    else {
        push @errors, catfile($File::Find::dir, $_) . " !$!";
    }
}

# filter unreadable directories
# from the list of files
# returned by readdir() before
# processing the directory:
# 
sub preprocess {
    my @readables;
    
    for (@_) {
        if (!-r) {
            push @unreadables, catfile($File::Find::dir, $_) . " !not readable";
        }
        else {
            push @readables, $_;
        }
    }

    return @readables;
}


# post-directory processing:
# 
sub postprocess {
    unless (@unreadables or @errors) {
        return;
    }
    print "$_\n" for (@unreadables, @errors);
    @unreadables = @errors = ();
}

find(
    {
        wanted      => \&wanted,
        preprocess  => \&preprocess,
        postprocess => \&postprocess,
    },
    $directory
);

print "$directory size: $size\n";