There's a neat trick if you want to find out what an option does, in terms of perl code: use B::Deparse: 
$ perl -MO=Deparse -le 'print 1'
BEGIN { $/ = "\n"; $\ = "\n"; }
print 1;
-e syntax OK
$ perl -MO=Deparse -ne 'print 1'
LINE: while (defined($_ = <ARGV>)) {
    print 1;
}
-e syntax OK

[download]

This shows how to get the semantics of -l and -n.

In reply to Re: Setting -l for a block by moritz
in thread Setting -l for a block by rovf

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