Fix shebang to /usr/bin/perl

EUMM will not replace "#!/usr/bin/env perl" with the path to the real
perl. This makes a script with such shebang less compatible with
environments with multiple perls.
So the shebang is fixed to /usr/bin/perl
DZ: add authordep for Pod::Weaver::Section::Contributors

This ease initial install of dzil build environment for contributors.