Coming up for your monk day is not new! This is your second post and again you have failed to format your node and have ignored the mess in the preview. Are you going to ignore any questions in replies as you did last time?

Do you really intend the assignment $cell = $sheet->... in the first and following if expressions?

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.