Having Major Problems With My Insert Query Logic

I have a perl program that is looping through a hash of a hash. I need to Update any existing records but also insert any new records in the table using collected data in the hash.

Life would be very simple if it was possible to use a Where Clause in an Insert statement but not does not work.

Here is some example code from my program:
sub Test{
foreach my $table(keys %$HoH){
foreach my $field(keys %{$HoH->{$table}}){
if($table eq "CPU"){
my $CPUstatement = "INSERT INTO CPU(CPUNumber, Name, MaxClockSpeed, SystemNetName)
Values ('$field',
'$HoH->{CPU}{$field}{Name}',
'$HoH->{CPU}{$field}{MaxClockSpeed}' ,
'$HoH->{Host}{SystemNetName}')";
print "$CPUstatement
";
if ($db->Sql($CPUstatement))
{
print "Error on SQL Statement
";
Win32::ODBC::DumpError();
}
else
{
print "successful
";
}
}
}


}
}

Thanks,
Laura