Improve pversion

bin/pversion

@@ -1,5 +1,9 @@
 #!/usr/bin/env perl
+use strict;
+use warnings;
+
 my $module = shift;
+die "Usage: pversion Some::Module" unless $module;
 
 package LETO::PVERSION; # for modules which won't let you use 'em in %main::
 eval "use $module";