use strict;

my $DB;
my @DB = qw(DB1 DB2);

{
   $DB = select_db();
   redo unless grep {$_ eq $DB} (@DB,'Q');
}
   
die if $DB eq 'Q';

sub select_db {
   print "Select a database: ";
   chomp($_ = <STDIN>);
   return $_;
}