[ Note: The following is from the author of Perl, Larry Wall. ]
My interpretation of the GNU General Public License is that no Perl script falls under the terms of the License unless you explicitly put said script under the terms of the License yourself. Furthermore, any object code linked with uperl.o does not automatically fall under the terms of the License, provided such object code only adds definitions of subroutines and variables, and does not otherwise impair the resulting interpreter from executing any standard Perl script. I consider linking in C subroutines in this manner to be the moral equivalent of defining subroutines in the Perl language itself. You may sell such an object file as proprietary provided that you provide or offer to provide the Perl source, as specified by the GNU General Public License. (This is merely an alternate way of specifying input to the program.) You may also sell a binary produced by the dumping of a running Perl script that belongs to you, provided that you provide or offer to provide the Perl source as specified by the License. (The fact that a Perl interpreter and your code are in the same binary file is, in this case, a form of mere aggregation.) This is my interpretation of the License. If you still have concerns or difficulties understanding my intent, feel free to contact me.