Sorry, I missed the task. The following should work:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

chomp (my @lines = <>);
for (0..$#lines) { $lines[$_-1] = undef if ($lines[$_] =~ /fail/)};
@lines = grep (defined, @lines);
print Dumper \@lines;
[download]