#!/usr/bin.perl -w
use strict;
use File::Find;

my $byte_total;
my $file_total;

find (\&sum_bytes, "C:/temp");

sub sum_bytes
{
    return() unless (-f $File::Find::name);
    
    $byte_total += -s _; # not a typo! 
                         # "_" different than "$_"!
                         # see [id://951317]
    $file_total++;
}

print "total bytes in C:/temp: $byte_total in $file_total files\n";

# prints on my Windows system:
# total bytes in C:/temp: 656201485 in 2554 files