sub query {
   my ($str,@argv) = @_;
   my $answer;

   while (1) {
      print "$str ", $argv[0] ? "[$argv[0]]: " : ": ";
      chomp($answer = <STDIN>);
      last unless @argv;
      last if grep $answer =~ /^\Q$_\E$/i, @argv;
   }
   return $answer;
}
[download]

last if grep $answer eq $_, @argv;
[download]

UPDATE:
Ahhh, i missed that you were allowing case insensitive answers via the regex. Here is another version that uses lc to match upper and lower cases. This code also fullfills the requirement of allowing the user to pick a default option. I missed that one the first time around ;)

sub query2 {
   my ($str,@argv) = @_;
   my $answer;

   while (1) {
      print "$str ", $argv[0] ? "[$argv[0]]: " : ": ";
      chomp($answer = <STDIN>);
      return $answer if !@argv or grep lc($answer) eq lc($_), @argv;
      return $argv[0] unless $answer;
   }
}
[download]

$answer = $default if ($answer eq "");

# with this instead
$answer ||= $default;
[download]

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)