More on use of the -x option: By itself, -x tells pp to run the specified Perl program. No arguments are supplied. This is attempt detection of modules (and libraries) loaded at run time. Sometimes, without arguments, your program will not load all - or even any - additional modules and/or libraries. Your program might even exit with a non-zero status. To work around these problems, there is the --xargs option to supply arguments to you program so that it will run "normally".