use File::Spec;
my $path = File::Spec->catfile("C:", "Dir1", "Dir2", "Dir3", "KeepMe");
my $base = File::Spec->catdir("C:", "Dir1", "Dir2", "Dir3");
# or
my $base = File::Spec->catdir("C:", "Dir1", "Dir2", "Dir3");
my $path = File::Spec->catfile($base, "KeepMe");