Another handy thing to know about is B::Deparse which will dump out the code as perl interprets it. If you use it with your oneliner you can see both print calls (from your argument to -e and the implicit one from -p in the generated continue block).

$ perl -MO=Deparse -pe 'print'
LINE: while (defined($_ = <ARGV>)) {
    print $_;
}
continue {
    die "-p destination: $!\n" unless print $_;
}
-e syntax OK
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Depending on what you're trying to figure out there's options to B::Deparse which can be useful like -p to add explicit parens everywhere (-MO=Deparse,-p,-q is another handy variant).