In addition to the links above from t0mas, the way I have used in the past is via cgi->tmpFileName and using File::Copy,

A subroutine example is below, msg me if you cant work out which bits might be useful.

P.S I have a suspicion setting the umask to 000 might not be a good thing but this sub is renaming the files...

sub storeFiles {
    my $self = shift;
    my $cgi = shift;
    my $mode = shift; # going to be insert or update

    my $fileerror = '0';
    my @filecols = ('DOC_1', 'DOC_2', 'IMG_1', 'IMG_2', 'IMG_3', 'IMG_
+4');
    my $umm = umask(000); 

    foreach my $doc (@filecols) {
        if ($cgi->param($doc)) {
            # if insert this is an add, else a replace action for upda
+tes

            my $longfile = $cgi->param($doc);
            my $tempfile = $cgi->tmpFileName($longfile);
            my $size = -s $tempfile;
             
            if (($size < 1) || ($size > 2000000)) {
                $fileerror = '1';
                last;
            }

            $longfile =~ s/ //g;                            # strip sp
+aces
            $longfile =~ s/^(.*[\/\\:])*([^\/\\:]+)$/$2/;   # remove p
+ath      

            if ($longfile !~ /\./) {
                $fileerror = '2';
                last;
            }

            $longfile =~ s/\.(?=.*\.)//g;                   # substitu
+te all but last dot (courtesy of L.Rosler)

            my ($f, $ext) = split /\./, $longfile;

            if (!$self->_isValidFile($doc, $ext)) {
                $fileerror = '3';
                last;
            }

            my $newfile = $DATA_DIR . $self->{'PAGE'}[2] . "/" . $self
+->{'DOCID'}[2] . $doc . "." . $ext;
            eval {
                copy ($tempfile, $newfile) or die "cant copy temp *$te
+mpfile* to new *$newfile* $! \n longfile is $longfile";
            };
            if ($@) {
                $fileerror = '4';
                last;
            } else {
                $self->{$doc}[2] = $self->{'DOCID'}[2] . $doc . "." . 
+$ext;              
            }
        } elsif ($cgi->param("exists$doc")) {
            $self->{$doc}[2] = $cgi->param("exists$doc");
        } else {
            $self->{$doc}[2] = '';
        }

        if (($cgi->param("chk$doc")) && (!$cgi->param($doc))) {
            # unlink file if update checkbox is checked        
            my $page = $self->{'PAGE'}[2];
            if (($page == 22) || ($page == 26) || ($page == 27)) {
                my $dir = "../data/$page";
                opendir (DIRH, $dir) or Util->showError("Can't Open de
+signated directory $dir $!");
                my @files = grep /^$self->{'DOCID'}[2]$doc/, readdir D
+IRH;
                @files = map ("$dir/$_", @files);
                closedir DIRH;
                unlink @files or Util->showError("oops cant unlink you
+r chosen files @files $!");
            }
            $self->{$doc}[2] = ''; 
        }
    }
    umask($umm);
    return $fileerror;
}
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