perlrun says of -n:

causes Perl to assume the following loop around your program, which makes it iterate over filename arguments somewhat like sed -n or awk: 
  LINE:
    while (<>) {
        ...             # your program goes here
    }

[download]
So, perl replaces '...' with jwkrahn's '}{print $.'.

Make sense now?

In reply to Re^3: one liner - open file and read by FunkyMonk
in thread one liner - open file and read by baxy77bax

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