Here is a version based on TedYoung's but using a circular buffer which I think is a little more efficient. Need to find a really big file to do some benchmarks.

#!/usr/bin/perl
use strict;
use warnings;

sub tailFile {
   my ($file, $lines) = @_;
   open F, $file or die $!;
   my @lines;
   $#lines=($lines-1);
   my $i;
   while (<F>) {
      $lines[$i++] = $_;
      $i = 0 if $i == $lines;
   }
   close F;
   # this works but not sure if this is safe using pre-dec
   # and var on same line see perlmonks nodes passim
   return @lines[$i--..$#lines, 0..$i]
}

print (tailFile ("/etc/passwd", 10));
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Cheers,
R.