chdir $file;
  chdir $dir;
[download]

Can you explain the purpose of that?

ISTM that your code has too many statments. Here's an SSCCE

#!/usr/bin/env perl 
use strict;
use warnings;
use Test::More tests => 3;

# Do all this in /tmp because we don't want permission trouble or to
# pollute real dirs while testing
chdir '/tmp';
my $dir = 'VEHICLES';
my @files = qw/CARS BIKES/;

mkdir $dir;
ok (-d $dir);

chdir $dir;

foreach my $subdir (@files) {
    mkdir $subdir;
    ok (-d $subdir);
}
[download]

Running gives:

$ ./ex.pl
1..3
ok 1
ok 2
ok 3
$ tree VEHICLES/
VEHICLES/
├── BIKES
└── CARS

2 directories, 0 files
$