> my @x = <FH>;
> @x = @x[($#x-100>0?$#x-100:0)..$#x];

##</code><code>##

open LOG,"<","/some/log" or die $!;
seek LOG,-50000,2;  # go to 50K from the end (assuming your log-lines have 500 or less characters)
my @lines = <LOG>;  # get all from there
splice @lines => 0, -100;  # see [Abigail-II]'s comment
close LOG;

print @lines;

##</code><code>##

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.