とりあえずFCLOSE(FID)をもう一個(作法知らないんで斟酌して)

try
FID = FOPEN("z:\hagehage.txt", F_READ or F_WRITE)
FPUT(FID , "ピロピロ" )
FCLOSE(FID)
except
print TRY_ERRMSG
FCLOSE(FID)     // ←追加
endtry
fend