#!/usr/bin/perl

# https://perlmonks.org/?node_id=1218012

use strict;
use warnings;

my $dirname = 'some/test';
my $outputfile = 'some.output.name';
local @ARGV = grep -f, glob "$dirname/*";
@ARGV or die "no files in $dirname";
open my $out, '>', $outputfile or die "$! opening $outputfile";
print $out $_ while <>;
close $out;