Please read Writeup Formatting Tips, the code in your posts is quite difficult to read.

This has probably nothing to do with your problem, but I'd suggest that you put a couple of markers around the variables you print, like in:

if ($success){
   print "Changed [$oldname] to [$newname]\n"
}
else {
   print "Failed to rename [$oldname] to [$newname] $!\n";
   exit
};
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just to be sure that there aren't stray trailing spaces wandering in your string. You could also go deeeper trying to see some hex dump of the strings, for example with:

sub hex_dump {
   unpack "H*", $_[0];
}
print "\$oldname = [", hex_dump($oldname), "]\t";
print "\$newname = [", hex_dump($newname), "]\n";
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If you don't want to check these hex dumps, you can ensure that your filename only contains letters, digits and dots:

$newname =~ tr/a-zA-Z0-9\.//cd;
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Back to your particular case: are you sure that the destination file -- i.e. 573427RSSt.csv -- does not exist or, if it exists, it is writeable?