Me personally, or the generally accepted way? My untested, "I hate answering these kinds of questions" way:

my $packname = 'Some::Module';
$packname =~ s!::!/!g;
$packname .= '.pm';
my $path = grep { -e "$_/$packname" } @INC or
    die "Can't find $packname in \@INC";

my $moduletext = '';
{
    local (*INPUT, $/);
    foreach my $file ($0, $path) {
        open( INPUT, $file ) or die "Can't open $file: $!";
        $moduletext .= <INPUT>;
    }
}

# almost ruined the joke here
require File::Temp;
my ($temphandle, $tempfile) = File::Temp::tempfile();
print *$temphandle $moduletext;
exec $moduletext;
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Update: Yes, I'm finding the module, reading it, appending it to the current program, writing the whole thing to disk, and calling exec on it. I didn't say it was the *best* solution, only the most flippant that came to mind. (Especially since it has a potential infinite loop. :)