First of all you should convert your code using a loop, like below. Then it gets tidy enough to make changes fast and avoid a lot of minor errors which are likely in repetitive code.

Should your output be XML ("output.xml")? Because it isn't yet. Have a look on XML::Simple's function xmlout() for that.

my @CELLS = ( 'pisbn', 'isbn', 'rendition', ...);
my %bookdata;

# [...]

for my $n (0..13) {
    if($cell = $sheet->{Cells}[$i][$n]) {
        my $val = $cell->{Val};

        #If you would need the data for later:
        $bookdata{@CELLS[$n]} = $val;

        #print"\n--", $val;
        $getfile = $val;
    }
}
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PS: Could you use <readmore> tags for code of this length in the future, please.

Update: Are you aware that your code overwrites the output file for every row ($i iteration) and sheet? This could be one of you main problems.