Making a big old map

#!/usr/bin/env perl
for my $y (0..20){
    for my $x (0..27){
        my $url = sprintf "http://www.paris.org/Maps/Map4/gifs.h/%02d.%02d.gif", $x, $y;
        system("wget '$url' -O '$y.$x.gif'");
    }
}
system("montage -tile 28x21 -geometry 100x100+0+0 *.gif map.gif");