$ cat -n AlwaysRun.pm
     1  package AlwaysRun;
     2  
     3  use Carp qw(:DEFAULT cluck);
     4  
     5  cluck "$0 $$: I am begun at " . localtime();
     6  
     7  1;

$ export PERL5OPT=-MAlwaysRun

$ perl -E 'say "howdy"'
-e 4574: I am begun at Thu Mar  8 22:55:52 2012 at AlwaysRun.pm line 5
        require AlwaysRun.pm called at -e line 0
        main::BEGIN() called at AlwaysRun.pm line 0
        eval {...} called at AlwaysRun.pm line 0
howdy