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

my @array;
my $PreviousLines = 4;
while (<DATA>) {
	chomp;	
	if (/xyz/) {
		print join "\n", @array;
		print "\n\n";		
	}else{
		push @array, $_;
		if (@array > $PreviousLines ) {
			# delete first element 
			splice @array, 0,1;
		}
		
	}	
}