ORA-00933 Error for to_char formatting PLSQL

I have the following codes:

IF nvl(p_value, 0) >= 0 THEN
      l_currency_prefix := 'scc.currency_prefix_pos';
      l_currency_suffix := 'scc.currency_suffix_pos';
    ELSE
      l_currency_prefix := 'scc.currency_prefix_neg';
      l_currency_suffix := 'scc.currency_suffix_neg';
    END IF;

l_query := 'SELECT nvl('||l_currency_prefix||', '')'
                       ||'trim(to_char('||p_value||
                                       ',scc.currency_format
                                        ,'||'NLS_NUMERIC_CHARACTERS=' || 'scc.decimal_group_separator'||'))'
                       ||'nvl('||l_currency_suffix||',  '')
              FROM gss.gss_currency_locale scc
             WHERE scc.country_code =' ||p_country_code||
              'AND scc.currency_code ='|| p_currency_code||
              'AND rownum=1';

and here is the dbms output for l_query:

SELECT nvl(scc.currency_prefix_pos, ')trim(to_char(10000,scc.currency_format
                                            ,NLS_NUMERIC_CHARACTERS=scc.decimal_group_separator))nvl(scc.currency_suffix_pos, ')
                  FROM gss.gss_currency_locale scc
                 WHERE scc.country_code =USAND scc.currency_code =USDAND rownum=1

However, it keep showing an ORA-00933 errors. I debug these piece of code for few hours and could not find where is the errors. Could some one please provide some advice on this?

Solution

Now some of the problems are obvious. You need something like this:

l_query := 'SELECT nvl('||l_currency_prefix||',
                       ||'trim(to_char('||p_value||
                                       ',scc.currency_format || ')' ||
              FROM gss.gss_currency_locale scc
             WHERE scc.country_code = ''' ||p_country_code|| '''' ||
              ' AND scc.currency_code = '''|| p_currency_code|| '''' ||
              ' AND rownum=1';

(I'm not sure if that is 100 percent correct.)

Usually, when creating queries this way, I use replace() instead of direct substitution. Something like:

l_query := 'select nvl(@currency_prefix, trim(@p_value, @currency_format))
from . . . ';
l_query := replace(l_query, '@currency_prefix', l_currency_prefix);
l_query := replace(l_query, '@p_value', p_value);
. . .

I find that this approach makes it much easier to maintain the code and to see what it is doing.