$re = '/(\'Your )(.*?)( were successfully )(<strong>edited<\/strong>\.\')/m';
$str = '\'Your package were successfully <strong>edited</strong>.\'
\'Your group were successfully <strong>edited</strong>.\'
\'Your subscriber were successfully <strong>edited</strong>.\'';
$subst = "L10n\:\:message\('action.label', array\('action' => L10n\:\:label\('edit'\), 'label' => L10n\:\:label\(MODULE\)\)\)";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php