#! perl -w
 my @dbs = <DATA>; 
 my $db= "\n";

print "Select DB from:\n @dbs or Q to quit:" 
      and $db = uc(<>) 
          while( $db eq "\n" || "@dbs\nQ\n" !~ m/$db/s);
chomp $db;

$db eq 'Q' and die "Quiting...\n";

print "\n$db selected\n";

__DATA__
DB1
DB2

##</code><code>##

C:\test>190748
Select DB from:
 DB1
 DB2
 or Q to quit:
Select DB from:
 DB1
 DB2
 or Q to quit:fred
Select DB from:
 DB1
 DB2
 or Q to quit:db2

DB2 selected

C:\test>190748
Select DB from:
 DB1
 DB2
 or Q to quit:q
Quiting...

C:\test>