moodle/blocks/search/config_global.html

<div style="text-align:center;">
  <label for="block_search_text">Search label</label>
  <input id="block_search_text" type="text" name="block_search_text" value="<?php 
    if(isset($CFG->block_search_text)) {
        p($CFG->block_search_text);
    } else {
        p("Search Moodle");
    } ?>"/><br/>
  
  <label for="block_search_button">Button label</label>
  <input id="block_search_button" type="text" name="block_search_button" value="<?php 
    if(isset($CFG->block_search_button)) {
        p($CFG->block_search_button);
    } else {
        p("Go");
    } ?>"/><br/><br/>
  
  <input type="submit" value="<?php print_string('savechanges'); ?>" />
</div>