use strict;
use warnings;

use File::Find::Rule;

my $target = 'C:\temp';

my $rule = File::Find::Rule->new;
$rule->file;            # Look for files (-f test)
$rule->name('*.csv');   # Look for filenames ending in .csv
$rule->size(<5500);     # Look for a size of less than 5500 bytes

my @files = $rule->in($target); 
# The @files array will have the files that meet the 'rules' above.