#!/usr/bin/perl

print ++$i, " $_" for <>;
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Put the above in a file, make it executable, and call it within vi as :1,17!script and it adds numbers to the lines you selected. Should be simple to go from there to whatever you want perl to do to those lines.

The line you select in vi will be fed to your script on STDIN and vi will replace those lines with whatever your script outputs.