Short answer: I'm almost positive that keys and values will always return hash entries in the same order, until the hash is modified. If you're really concerned about it, you can do something like this:

my($l_tablename, %l_data) = @_;
my(@fields, @values);
push(@fields, $_) && push(@values, $1_data{$_})
    for(keys %1_data);

my($1_prepare);
{
    local $" = ','; # eliminate join statements
    $1_prepare = qq(
        INSERT INTO $1_tablename (@fields) 
        VALUES (@values)
    );
}
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Long answer:

1. The first literal character in a variable can't be a numerical value. So "1_" will have to go! =)
2. In your original code, you assign a hash to a shift statement. This won't work because you'll only get the first value from the list you pass. The assignment arrow operator => acts the same as a comma in a list, and lists flatten. So something like this will happen:
   

   @list = ('arg1', ('field1' => 'value1', 'field2' => 'value2'));
   # above same as:
   @list = ('arg1', 'field1', 'value1', 'field2', 'value2');
   
   $table = shift(@list);  # 'arg1'
   %fields = shift(@list); # 'field1'
   [download]

   The last statement, in order to put all the remaining values from @list into %fields should read: %fields = @list;
3. Writing a function to prepare generic insert statements is generally a bad idea. This is just asking for people to call your function with invalid table names, field names, and data types. If the database itself changes, it becomes more difficult to fix the code because you have to track down every place where this subroutine is being called.

There's probably a better way to do what you're trying to do. Writing an insert subroutine for each table in the database that allows new records might be a better solution. If you are really ambitious, you can even write an OO wrapper for each table, with select, insert, update, and delete methods. Then you can write things like:

    my $person = new MyDB::Person(4);
    $person->update(name => 'John B.');
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instead of     &update('person', { pk => 4, name => 'John B.' });

...or whatever. Just a few thoughts for you to mull over. {g}