$dir = "VEHICLES";
@files = ('CARS', 'BIKES');
if(not -d $dir)
{
    mkdir ($dir) or die "can't mkdir $dir: $!";
}
chdir ($dir) or die "can't chdir to $dir: '$!'";
foreach $file(@files)
{
  if (not -d $file)
  {
      mkdir $file or die "(loop) can't mkdir $file: '$!'";
  }
}