How to delete all Persistent variables when a page is loaded?
It is considered bad practice to delete all the persistent variables whose name starts with the short name of the module. There could be a module whose short name starts with that short name; in that case you would be removing the persistent variables of that module.
For example, given the Views module, there could be a Views Enhancer module. Deleting all the persistent variable matching the SQL pattern '%views_%' would mean deleting the persistent variables of both modules.

Instead, you should have a list of all the persistent variables your module uses. (That is not hard, since you are writing the code of your module.) Using that list (for example, contained in $variables), a code like the following would delete all the variables.

  global $conf;

  db_delete('variable')
    -&gt;condition('name', $variables, 'IN')
    -&gt;execute();
  cache_clear_all('variables', 'cache_bootstrap');

  foreach ($variables as $name) {
    unset($conf[$name]); 
  }


This is, essentially, the code of variable_del() adapted to delete a list of variable names contained in $variables.

You could also use that code to implement a function your module uses.

function variable_delete_multiple(array $variables) {
  global $conf;

  db_delete('variable')
    -&gt;condition('name', $variables, 'IN')
    -&gt;execute();
  cache_clear_all('variables', 'cache_bootstrap');

  foreach ($variables as $name) {
    unset($conf[$name]); 
  }
}