that's his use case:

lanx@lanx-1005HA:~$ export PERL5OPT="-Mstrict -Mwarnings -MData::Dump 
+-Mfeature=say"
lanx@lanx-1005HA:~$ perl
say "huhu";
dd [1,2,3]
__END__
huhu
[1, 2, 3]
[download]

of course he could alias perl to restrict the effect to the interactive shell only, but I'd like to know if PERL5OPT is usuable after all.