To add to the excellent advice by Athanasius, now would also be a good time to learn about grep:

my @downloads = grep { !/^asdf$/ } @file_list;

print "Downloading: @downloads\n";
[download]

It's also worth noting that if you truly want to exclude a literal string, you don't need a regex at all, so you could also do:

This works just as well if asdf is in a variable.

my $exclude   = 'asdf'; # Maybe user input or other program logic
my @downloads =  grep { $_ ne $exclude } @file_list;
[download]