Looks like your Excel doesn't understand UTF-8 encoded strings. So, you could try to convert your $temp into one of the other likely candidate encodings, which are "UCS-2LE" (or "UTF-16LE" for that matter... though Windows more often uses UCS-2), or "cp1252" (the Windows variant of the legacy encoding "iso-8859-1").

In other words, before you set your cell's value, insert a line

$temp = encode("UCS-2LE", $temp);
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or

$temp = encode("cp1252", $temp);
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and see if that helps...

The routine encode() is from the module Encode, so you'll need to add "use Encode qw(encode);" somewhere near the beginning of the script.