use strict;
use warnings;
my $match = qr /Match/;
my $extra = qq(EXTRA\nEXTRA\n);
my @extras = (q()) x 3;
my $in  = 3;
my $out = 0;
while (my $line = <DATA>) {
    $out = ($out+1) % 4;
    print $line, $extras[$out];
    $in  = ($in +1) % 4;
    $extras[$in] = ($line =~ /$match/)? $extra : q();
}
__DATA__
a
b
Match1
Match2
c
d
e
f
g
Match3
h
i
j
k