var patterns = [
    /https?:\/\/.+?\/.+?\/.+?_desc_(.+)\.html$/
];

console.log(document.referrer);
document.addEventListener('DOMContentLoaded', function() {
    var prevUrl = document.referrer;
    if (!prevUrl) {
        return;
    }
    var pattern;
    for (var i = 0; i < patterns.length; i++) {
        pattern = patterns[i];
        match = prevUrl.match(pattern);
        if (match && match.length == 2) {
            searchVal = match[1];
            var searchField = document.querySelector('#MSearchField');
            searchField.value = searchVal;
            break;
        }
    }
});