Because t() is designed for handling code-based strings, in almost all cases, the actual string and not a variable must be passed through t().
Extraction of translations is done based on the strings contained in t() calls. If a variable is passed through t(), the content of the variable cannot be extracted from the file for translation.
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Block Titles
Block titles should show up in admin/build/translate on their own. There should not be any need to add t() strings to the template.
Be careful with t() and variables, as I am pretty sure what you have suggested is dangerous. Read the Drupal API documentation to learn more.
http://api.drupal.org/api/drupal/includes--common.inc/function/t/6
Because t() is designed for handling code-based strings, in almost all cases, the actual string and not a variable must be passed through t().
Extraction of translations is done based on the strings contained in t() calls. If a variable is passed through t(), the content of the variable cannot be extracted from the file for translation.
Incorrect:
<?php
$message = 'An error occurred.';
drupal_set_message(t($message), 'error');
$output .= t($message);
?>
Correct:
<?php
$message = t('An error occurred.');
drupal_set_message($message, 'error');
$output .= $message;
?>