use Modern::Perl;

my @l = system(`ls -1b`);
my $c = 0; # toggle for odd/even lines
for (@l){
    chomp;
    my $bg = $c ? "#eee" : "#ccc";
    say qq| <p style="font-family:mono;background:$bg">$_</p> |;
    $c = 0 if $c++ == 1;
}