don't need $lines -- $. does it for you (see perlvar) 
perl -le 'open FILE, "/etc/passwd"; @_=<FILE>; print $.'

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And (similar to QM's golf reply: 
perl -lne 'END{print $.}' /etc/passwd

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In reply to Re^2: Count number of lines in a text file by davidrw
in thread Count number of lines in a text file by Scott7477

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