There are a few things about your code as posted that seem odd (i.e. not good):

• You open MARKER for output inside the "get_pocus" subroutine, but close it outside the subroutine.
• You connect to the database before going into the  while (<LIST>) loop at the end, but disconnect inside the while loop.
• You prepare a statement on each iteration of that while loop with a quoted parameter in the "where" condition, whereas you should prepare the statement before the while loop with a "?" placeholder, and just call "execute" on that statement in each iteration, passing the parameter value to the "execute" call.

Also, it looks like the usage is just a matter of providing a single number between 1 and 10. It would make more sense to have that as a command-line arg:

my $Usage = <<ENDUSE;
Usage: $0 N
  where N is a number between 1 and 10:
  1 : Alzheimer disease
  2 : Bardet Biedl
  3 : Breast cancer
  ...
ENDUSE

die $Usage unless ( @ARGV == 1 and $ARGV[0] =~ /^\d+$/ 
                    and $ARGV[0] > 0 and #ARGV[0] < 11 );
my $choice = shift;

...
[download]

This way, it's easier to run the script either interactively or from another process, because the information that the script needs from the user is part of the command line.