use 5.16.2;
use warnings;

sub usage { die "usage: $0 file.xlsx name [out.csv]\n"; }

my $xls = shift or usage;
my $sht = shift or usage;
my $out = shift // $xls;
   $out =~ s/\.xlsx$/.csv/i;

use Spreadsheet::Read;
use Text::CSV_XS;

my $csv = Text::CSV_XS->new ({ binary => 1, eol => "\r\n", auto_diag => 1 });
open my $fh, ">", $out or die "$out: $!\n";

my $book  = ReadData ($xls) or die "$xls: $!\n";

my $sheet = $book->[$book->[0]{sheet}{$sht}];

foreach my $row (1 .. $sheet->{maxrow}) {
    $csv->print ($fh, [ Spreadsheet::Read::row ($sheet, $row) ]);
    }
close $fh;