use CGI;
use CGI::Carp qw(fatalsToBrowser);
use Fcntl qw(:DEFAULT :flock);
use Archive::Zip;

my $DataPath = '/MyDataDirectory';

# ...

my $query = new CGI;
my $InpFile = $query->param('filData');
	# 'filData' is the name of the form's file selection
	# control.
my $FileName = reverse($InpFile);
$FileName =~ s/\\.*//;
	# Assuming a Windows client (\), strip client's path info
	# from file name.
$FileName = reverse($FileName);
	# There's GOTTA be a better way ...
$FileName eq 'zipfile.zip' or die 'Wrong file.';
undef $/;
my $ZipContents = <$FileName>;
$/ = "\n";
OpenLockTruncate (*ZIPFILE, "$DataPath/temp/zipfile.zip");
my $OldDefaultHandle = select(ZIPFILE);
$| = 1; # Force flush without closing/unlocking file.
select($OldDefaultHandle);
print ZIPFILE $ZipContents;
OpenLockTruncate (*INPFILE, "$DataPath/temp/unzipped.dat");
close INPFILE;
my $zip = Archive::Zip->new("$DataPath/temp/zipfile.zip");
my $file = ($zip->memberNames)[0];
$file eq 'unzipped.dat'
	or die "Can't find correct data file in zip.";
$file = $zip->memberNamed($file)
	or die "Can't access data file in zip.";
$file->extractToFileNamed("$DataPath/temp/unzipped.dat") == AZ_OK
	or die "Unable to extract data file.";

# ...

sub OpenLockTruncate {
    local *FH = $_[0];
    sysopen (FH, $_[1], O_RDWR|O_CREAT, 0600)
	or die "Can't open $_[1]: $!";
    flock (FH, LOCK_EX) or die "Can't lock $_[1]: $!";
    seek (FH, 0, 0) or die "Can't rewind $_[1]: $!";
    truncate (FH, 0) or die "Can't truncate $_[1]: $!";
    return 1;
}