The bottom loop should be

for (@$sales_inserts) {
    my $table = shift(@$_);
    my $sth = $dbh->prepare('
        INSERT INTO '.$dbh->quote_identifier($table).' (
                   ItemID, Day, Revenue, Count
               ) VALUES (
                   ?, ?, ?, ?
               )
    ');
    $sth->execute(@$_);
}
[download]

my %sth_cache;
for (@$sales_inserts) {
    my $table = shift(@$_);
    my $sth = $sth_cache{$table} ||= $dbh->prepare('
        INSERT INTO '.$dbh->quote_identifier($table).' (
                   ItemID, Day, Revenue, Count
               ) VALUES (
                   ?, ?, ?, ?
               )
    ');
    $sth->execute(@$_);
}
[download]