I am not sure my proposal will not create havoc elsewhere in your html (ie how robust it is) but have a look: 

use strict;
use warnings;
my $html = ">lt;amp; something else <gt;amp;something else ;
+";
$html =~ s|&(([^ ;]+;)+)| join '', map { "&$_;" } split /;/, $1 |ge;
print "$html\n";

[download]

UPDATE: Probably \w is more robust than [^ ;].

In reply to Re: Question for regex experts by hdb
in thread Question for regex experts by evgen-i

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