How about this (a suggestion of my colleague)? 
$_ = "test;a  <>amp;kap;&da;ma; &amp alfa&romeo & mich;";

while ( s/([&][^ ]*);(?!( |&|$))/\1AMPSEMICOLON/ ) {};
s/AMPSEMICOLON/;\&/g;

# Output:
test;a  &<>&&kap;&da;&ma; &amp alfa&romeo & mich;

[download]
As you see, this is not restricted to a particular list of html codes, and that is what I want!

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

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