Here is the progression of code that I took it from (note this is for tail and not the last $n matching lines but the change is minor).

    # tail
    perl -ne '$i=$.%5; $a[$i]=$_; END{print @a[$i+1..$#a,0..$i]}' file
    perl -ne 'END{print@a[$i+1..$#a,0..$i]}$a[$i=$.%5]=$_' file
    perl -ne 'END{print@a[$i+1..@a,0..$i]}$a[$i=$.%5]=$_' file
    perl -pe '$a[$i=$.%5]=$_}{print@a[$i+1..@a,0..$i]' file
    perl -pe '$_[$==$.%5]=$_}{print@_[$=+1..@_,0..$=]' file
[download]

Also, I left out -w on purpose for cases where there were less matches than $n. Try this:

    echo foo | perl -wpe 'your code here' file
[download]

That is also why I was able to get away with @a.

--
John.

Whoops, only tried mine with >=5 inputs. You are entirely correct.