This is very simple example, hopefully it is enough to get you going in the right direction.
use LWP::Simple;
my $fileIWantToDownload = 'http://perlmonks.com/images/blueperlmonkssm
+.gif';
my $fileIWantToSaveAs = 'monk_image.gif';
getstore($fileIWantToDownload, $fileIWantToSaveAs);