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;
    }
}