im_maybe_prepend_http

im_maybe_prepend_http   query_url

Prepends http to query_url unless it already starts with http://

Source code:

    set query_url [string tolower [string trim $query_url]]
    if { [empty_string_p $query_url] || [string compare $query_url "http://"] == 0 } {
	return ""
    }
    if { [regexp {^http://.+} $query_url] } {
	return $query_url
    }
    return "http://$query_url"