SQL> desc masking_emails
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 TABLE_NAME                                NOT NULL VARCHAR2(100)
 COLUMN_NAME                               NOT NULL VARCHAR2(100)
 NULABLE                                            VARCHAR2(1)
 DATETIME                                           DATE


the script:

create or replace procedure search_schema( p_string in varchar2 )
authid current_user
as
l_cols long;
l_where long;
l_cursor sys_refcursor;
l_cname varchar2(4000);

begin
dbms_application_info.set_client_info( '%' || p_string || '%' );
for x in ( select table_name from user_tables )
loop
l_cols := 'case when 1=0 then ''x'' ';
l_where := ' where ( 1=0 ';
for y in ( select '"' || column_name || '"' column_name
from user_tab_columns
where table_name = upper(x.table_name)
and (data_type in ( 'VARCHAR2' ) and DATA_LENGTH>6
 )
)
loop
l_cols := l_cols || ' when ' || y.column_name ||
' like sys_context(''userenv'',''client_info'') then ' ||
' ''' || y.column_name || '''';
l_where := l_where || ' or ' || y.column_name || ' like sys_context(''userenv'',''client_info'') ';

end loop;
open l_cursor for 'select ' || l_cols || 'else null end cname from ' ||
x.table_name || l_where || ') and rownum=1';
fetch l_cursor into l_cname;
if ( l_cursor%found  )
then
 dbms_output.put_line( x.table_name || ' ' || l_cname );
end if;
close l_cursor;
end loop;
end;
/