Perl/Questions

Write a one liner to dump out a module’s runtime dependencies… †

What would this return? †

$str = "This is a test";
$str2 = substr($str, -2); 

How would you interchange the keys and values to a hash like this: †

%hash = ( foo => 1, bar => 2, baz => 3);  # before
%hash2 = ( 1 => foo, 2 => bar, 3 => baz); # after

Which would you use and why? †

if (index($foo, "text to find") > -1) { # Option 1
if ($foo =~ /text to find/) {           # Option 1

Please explain the following and how you would re-write it: †

my @sorted_list = sort{str2time($b->{$sort_by}) <=> str2time($a->{$sort_by})} @payload;

How would you re-write this? Can you spot the typo? †

if (($aggregate->{m}->{rev}+$aggregate->{c}->{rec}) > 0 && ($aggregate->{m}->{imp}+$aggregate->{c}->{imp}) > 0) {
    $aggregate->{ecpm} = (($aggregate->{m}->{rev}+$aggregate->{c}->{rev}) / (($aggregate->{m}->{imp}+$aggregate->{c}->{imp}) / 1000));
}

What does this do and how would you do it differently? †

my %boost_factors = (
  map {
    my $l = $_ < 0
       ? (($_ + 10) * 10)
       : (($_ + 1) * 100);

    ($_, $_ && "$l%")
  } -9 .. 9
);

Explain and show how you would re-write (if needed) the following: †

• In some perl module far, far away

  CAMPAIGN: {
      last CAMPAIGN if
        # Don't show competing campaigns
           ($seen_competing_campaigns
          and grep defined, reverse @{$seen_competing_campaigns}{@{$c_data->{competing_campaigns} ||= []}})