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perl -e "for(glob '*.xls'){$o=$_; s/(\.xls)$/.old$1/i;rename $o,$_}"
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perl -e "for(glob '*'){next unless -f;@s=stat;unlink($_) if (time-$s[9])>60*60*48;}"
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perl -MFile::Find -e "find(sub{@s=stat;unlink if (time-$s[9])>60*60*48 && -f},'.')";