use List::Util qw(sum);
use Scalar::Util qw(looks_like_number);

use Test::More;

ok looks_like_number(1), 'Found a number.';
ok !looks_like_number('a'), 'Rejected a non-number.';
is_deeply [map {$_ + 1} (1,2,3,4)], [2,3,4,5], 'Correct mapping.';
is_deeply [grep {looks_like_number($_)} qw(a 1 b 2 c 3 d 4)], [1,2,3,4], 'Correct filter.';
cmp_ok sum(1,2,3,4), '==', 10, 'Sum was correct.';
cmp_ok sum_of_incremented_nums(qw(1 a 2 b c 3 d 4)), '==', 10, 'summed dirty list properly.';

# Integration:

sub sum_of_incremented_nums {
    return sum(map{$_+1} grep {looks_like_number($_)} @_);
}

##</code><code>##

./projectdir
            \
            \
             - projectdir/lib/
             - projectdir/bin/
             - projectdir/t/
             - projectdir/xt/
             - projectdir/README

##</code><code>##

#!/usr/bin/env perl

use strict;
use warnings;

use FindBin qw($Bin);

use lib "$Bin/../lib";

use MyModule;
...