.....
my ($urltop) = 'http://www.somewhere.com/';
my ($urltodir) = 'http://www.somewhere.com/folder/';

my(@matches) = ($content =~ /href="([^"]*)"/gi);
foreach my $match (@matches) {
        if ($match =~ /^http/i) {
                ## absolute leave alone
	} elsif ($match =~ /^\//) {
		$content =~ s/href="$match"/href="$urltop$match"/gi;
	} else {
		$content =~ s/href="$match"/href="$urltodir\/$match"/gi;
	}
}