use strict;

my $dbh = DBI->connect(XXXX);

runSomeQueries();

$dbh->disconnect();

sub runSomeQueries
{
   my $query = "select * from table";
   my $sth = $dbh->prepare($query);
   if ( $sth->execute() )
   while (my $data = $sth->fetchrow_hashref )
   { 
      runSomeSubQueries(some$$hash{ItemID});
   }
}

sub runSomeSubQueries
{
   my $itemID = shift;

   my $query = "select * from detail_table where ItemID = ?";
   my $sth = $dbh->prepare($query);
   $sth->execute($itemID);

}