#!perl
use strict;
use warnings;

sub read_file ($) {
    my $file = shift;
    if ( open my $in, '<', $file ) {
        local $/;
        return <$in>;
    } else {
        warn "can't read file $file: $!\n";
        return ();
    }
}

sub files_from_dir ($) {
    my $dir = shift;
    opendir( my $d, $dir ) or die "can't open dir $dir: $!\n";
    my @list = readdir $d;
    closedir $d;
    return map { -f (sprintf '%s/%s', $dir, $_) ? (sprintf '%s/%s', $dir, $_) : () } @list;
}

sub write_to_file ($@) {
    my $output = shift;
    open my $o, '>', $output  or die "can't write to file : $!\n";
    print {$o} @_;
    close $o or die "can't complete writing to file: $!\n";
}

write_to_file './output', map { read_file $_ } files_from_dir '/some/directory';