--- sql2xls.cgi	2010/12/28 13:56:16	27
+++ sql2xls.cgi	2012/12/27 12:57:01	28
@@ -224,6 +224,7 @@
 					warn "## heuristic date time: $1T$2\n" if $debug;
 					$worksheet->write_date_time( $row, $col, "$1T$2", $date_format );
 				} else {
+					$data = "'" . $data if $data =~ m/^=/; # escape data which looks like formula
 					$worksheet->write($row, $col, _c( $data ) );
 				}
 			}