Generally speaking I'm in favour of splitting as much logic as possible out into object-oriented modules.

#!/usr/bin/env perl

use strict;
use warnings;

# This could go into a separate ".pm" file.
{
    package DirectoryProcessor;
    
    use Class::Tiny { 
        script  => sub { $ENV{DIR_PROCESSOR_SCRIPT} || "echo -e" },
        verbose => sub { 0 },
    };
    use Getopt::Long qw( GetOptionsFromArray );
    
    sub process {
        my $self = shift;
        my ($dir) = @_;
        
        my $cmd = sprintf('%s %s', $self->script, $dir);
        chomp( my $ret = `$cmd` );
        print qq(Output: "$ret"\n) if $self->verbose;
    }
    
    sub process_all {
        my $self = shift;
        $self->process($_) for @_;
    }
    
    sub handle_argv
    {
        my $class = shift;
        my ($argv, $opt) = @_;
        
        $argv ||= \@ARGV;
        $opt  ||= {};
        
        GetOptionsFromArray($argv, $opt, 'script=s', 'verbose!');
        
        my $self = $class->new($opt);
        $self->process_all(@$argv);
    }    
}

# Here's the body of the script.
DirectoryProcessor->handle_argv;
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