sub install {
    my($from_to,$verbose,$nonono,$inc_uninstall) = @_;
    $verbose ||= 0;
    $nonono  ||= 0;

    my $bootstrapped = eval 'use Filesys::Type 0.02 (qw|fstype|); 1;'; # CPAN
    my $no_colons_in_basenames;

    my @DOSish_FSTs = qw(msdos umsdos vfat ntfs iso9660 smb FAT FAT32 CDFS NTFS);
=for COMMENTARY

    # Types of fs that can be returned by Filesys::Type::fstype would have been nice
    #   to have access to without breaking into the module's encapsulation. (this is IMHO
    #   nonoptimal design; these could/should have been exportable from the module).

=cut

    use Cwd qw(cwd);
    use ExtUtils::Packlist;
    use File::Basename qw(dirname);
    use File::Copy qw(copy);
    use File::Find qw(find);
    use File::Path qw(mkpath);
    use File::Compare qw(compare);

    my(%from_to) = %$from_to;
    my(%pack, $dir, $warn_permissions);
    my($packlist) = ExtUtils::Packlist->new();
    # -w doesn't work reliably on FAT dirs
    # UHH, FAT-type filesystems can be found on other than MSWin32 OS's. Huh? XXX
    $warn_permissions++ if $^O eq 'MSWin32';
    local(*DIR);
    for (qw/read write/) {
	$pack{$_}=$from_to{$_};
	delete $from_to{$_};
    }
    my($source_dir_or_file);
    foreach $source_dir_or_file (sort keys %from_to) {
	#Check if there are files, and if yes, look if the corresponding
	#target directory is writable for us
	opendir DIR, $source_dir_or_file or next;
	for (readdir DIR) {
	    next if $_ eq $Curdir || $_ eq $Updir || $_ eq ".exists";
            my $targetdir = install_rooted_dir($from_to{$source_dir_or_file});

            ++$no_colons_in_basenames if grep(fstype($targetdir) eq $_ , @DOSish_FSTs);

            mkpath($targetdir) unless $nonono;
	    if (!$nonono && !-w $targetdir) {
		warn "Warning: You do not have permissions to " .
		    "install into $from_to{$source_dir_or_file}"
		    unless $warn_permissions++;
	    }
	}
	closedir DIR;
    }
    my $tmpfile = install_rooted_file($pack{"read"});
    $packlist->read($tmpfile) if (-f $tmpfile);
    my $cwd = cwd();

    MOD_INSTALL: foreach my $source (sort keys %from_to) {
	#copy the tree to the target directory without altering
	#timestamp and permission and remember for the .packlist
	#file. The packlist file contains the absolute paths of the
	#install locations. AFS users may call this a bug. We'll have
	#to reconsider how to add the means to satisfy AFS users also.

	#October 1997: we want to install .pm files into archlib if
	#there are any files in arch. So we depend on having ./blib/arch
	#hardcoded here.

	my $targetroot = install_rooted_dir($from_to{$source});
        my $blib_lib   = File::Spec->catdir('blib', 'lib');
        my $blib_arch  = File::Spec->catdir('blib', 'arch');
	if ($source eq $blib_lib and
	    exists $from_to{$blib_arch} and
	    directory_not_empty($blib_arch)) {
	    $targetroot = install_rooted_dir($from_to{$blib_arch});
            print "Some files found in $blib_arch: we shall therefore be "
                . "installing files in $blib_lib into the architecture dependent "
                . "library tree\n";
	}

        chdir $source or next;
	find(sub {
	    my ($mode,$size,$atime,$mtime) = (stat)[2,7,8,9];
	    return unless -f _;

            my $origfile = $_;
	    return if $origfile eq ".exists";
	    my $targetdir  = File::Spec->catdir($targetroot, $File::Find::dir);
	    my $targetfile = File::Spec->catfile($targetdir, $origfile);
            my $sourcedir  = File::Spec->catdir($source, $File::Find::dir);
            my $sourcefile = File::Spec->catfile($sourcedir, $origfile);

            # Cope with installation of man files to FAT type filesystems (could
            # be installing to removable media formatted as vfat/FAT32 from a
            # UNIX OS, like GNU/Linux or Cygwin or *BSD, for example).
            if($sourcedir =~ m{ blib/man[31] }x and $no_colons_in_basenames) {
                my $formername = $targetfile;
                $targetfile =~s{::} {.}g;
                warn qq|INFO: "$formername"\n    => "$targetfile"\n|
                   , qq|for writing to the target location which is a|
                   , (' '.fstype($targetdir))
                   , qq| filesystem (no colons allowed).\n|;
            }

            my $save_cwd = cwd;
            chdir $cwd;  # in case the target is relative
                         # 5.5.3's File::Find missing no_chdir option.

	    my $diff = 0;
	    if ( -f $targetfile && -s _ == $size) {
		# We have a good chance, we can skip this one
		$diff = compare($sourcefile, $targetfile);
	    } else {
		print "$sourcefile differs\n" if $verbose>1;
		$diff++;
	    }

	    if ($diff){
		if (-f $targetfile){
		    forceunlink($targetfile) unless $nonono;
		} else {
		    mkpath($targetdir) unless $nonono;
		    print "mkpath($targetdir)\n" if $verbose>1;
		}
		copy($sourcefile, $targetfile) unless $nonono;
		print "Installing $targetfile\n";
		utime($atime,$mtime + $Is_VMS,$targetfile) unless $nonono>1;
		print "utime($atime,$mtime,$targetfile)\n" if $verbose>1;
		$mode = 0444 | ( $mode & 0111 ? 0111 : 0 );
		chmod $mode, $targetfile;
		print "chmod($mode, $targetfile)\n" if $verbose>1;
	    } else {
		print "Skipping $targetfile (unchanged)\n" if $verbose;
	    }

	    if (defined $inc_uninstall) {
		inc_uninstall($sourcefile,$File::Find::dir,$verbose, 
                              $inc_uninstall ? 0 : 1);
	    }

	    # Record the full pathname.
	    $packlist->{$targetfile}++;

            # File::Find can get confused if you chdir in here.
            chdir $save_cwd;

        # File::Find seems to always be Unixy except on MacPerl :(
	}, $Is_MacPerl ? $Curdir : '.' );
	chdir($cwd) or Carp::croak("Couldn't chdir to $cwd: $!");
    }
    $no_colons_in_basenames = undef;  # XXX ?
    if ($pack{'write'}) {
	$dir = install_rooted_dir(dirname($pack{'write'}));
	mkpath($dir,0,0755) unless $nonono;
	print "Writing $pack{'write'}\n";
	$packlist->write(install_rooted_file($pack{'write'})) unless $nonono;
    }
}