You're regexing with \.pm$, but you're globbing for *. Doesn't sound like something I'd do. Seems a lot more natural to me do to:

opendir my $dir, PLUGINS;
@scanners = map (-f $_ ? /^(.*)\.pm$/i : ()), readdir $dir;
closedir $dir;
# ..
    require "$_.pm";
[download]

That said, it seems like you're trying way too hard. The following is untested and may need some tweaking, but you get the idea.

{
    local @INC = PLUGINS;
    opendir my $dir, PLUGINS;
    eval qq(@{[ map -f && ? /^(.*)\.pm$/ && "use \Q$1\E;", readdir $di
+r ]});
    closedir $dir;
}
[download]

Update: had forgotten to actually put the plugins path into @INC.

Makeshifts last the longest.