For a small file (1 to 100 lines would qualify), you can just read the whole thing into an array at the start. Then you know how many lines you have. 
  my @lines = <TXTIN>;
  for (@lines[0..($#lines - 1)]) {
    s/yada/yadda/;
  }
  $lines[-1] =~ s/different/substitution/;

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In reply to Re: While.For loop noob query by Roy Johnson
in thread While.For loop noob query by jriggs420

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