use strict;
use XML::XSLT;

my $xmlFilename = 'input.xml';
my $xslFilename = 'input.xsl';
(my $outFilename = $xmlFilename) =~ s/\.xml$/\.csv/i;

my $xslt = XML::XSLT->new($xslFilename, warnings => 1);
$xslt->transform($xmlFilename);
print $xslt->toString;