use Data::Dumper;
my $aref = [1, 6, 2, 2, 7, 1, 6, 99, 99, 7];
my @new = ();
my $flag = 0;
for (@$aref) {
    $flag = 1 if (!$flag and $_==6);
    push @new, $_ if !$flag;
    $flag = 0 if ($flag and $_==7);
}
$aref = \@new;
print Dumper $aref;