promises again

# Original code, simplified without zip and email

package require promise
namespace path promise
set urls [list http://www.example.com http://www.tcl-lang.org]
proc print_done args {puts "All done!"}
proc save_file args {}
set promises  [lmap url $urls {
    [pgeturl $url] then [lambda {dir url http_state} {
        save_file $dir $url [dict get $http_state body]
    } /tmp $url]
}]
set gate [all $promises]
$gate done print_done


# Above example with additional requirement to run du in parallel
package require promise
namespace path promise
set urls [list http://www.example.com http://www.tcl-lang.org]
proc print_done args {puts "All done!"}
proc save_file args {}
set promises  [lmap url $urls {
    [pgeturl $url] then [lambda {dir url http_state} {
        save_file $dir $url [dict get $http_state body]
    } /tmp $url]
}]
lappend promises [pexec du -sk /tmp]; # Single line added
set gate [all $promises]
$gate done print_done