use strict;
use LWP::Simple qw(getstore head is_success);

my @allowed = ('text/html', 'image/gif');

my $content = (head($url))[0];
die "Invalid content type! Please check URL.\n"
    unless grep($content =~ /\Q$_\E/, @allowed);

FETCH: for(1..5) {
    if(is_success getstore($url, $output)) {
        printf "$output %d bytes OK\n", -s $output;
        last FETCH;
    } else {
        sleep 5;
    }
} continue {
    die "Unable to fetch and store: $!\n$url => $output\n";
}