I guess "File writing error" is due to messy data not parsed properly by parser module. Two runs I tested use almost same perl code (except a bit difference for multi-task requiring a submission script (batch jobs in PBS manager). Forgot to mention that XML::Parser also requires another Expat library (.so) to work properly. Just suspect that PBS cluster manager ignored the path in ENV or something related to dynamic library? tried to set ld_Library_Path in script, so far the error still persists. Any input is appreciated.