use if $VersionOS eq 'Win', Win32::OLE => 'CP_UTF8';

Note that this doesn't work under strict because Bareword "Win32::OLE" not allowed while "strict subs" in use; the :: prevents the LHS of the fat comma being autoquoted. So:

use if $VersionOS eq 'Win', 'Win32::OLE' => 'CP_UTF8';
# or
use if $VersionOS eq 'Win', 'Win32::OLE', 'CP_UTF8';
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