sub convert_unicode {
    use HTML::Entities;
    use Encode;
    my $str = shift;
    Encode::_utf8_off($str);
    return encode_entities(decode('utf8',$str));
}

use HTML::Entities;
use v5.10;
say encode_entities("&foo");

sub get_user_info {
    my $uid = shift;

    ...do a bunch of work to get the user info...

    ...HTML encode the data...

    ...return the encoded data...
}

sub do_something {
    my $uid = shift;
    my $info = get_user_info($info);

    my $data = ...something incorporating $info...

    # Whoops, double encoded.
    return encode_entities($data);
}