my %k = qw(l < g > & &);
print "$_ to ".s/(&)amp;|&(l|g)t;/$k{$+}/reg.$/
   for qw( &amp; &amp;lt; &amp;gt; &lt; &gt; );

##</code><code>##

&amp; to &
&amp;lt; to &lt;
&amp;gt; to &gt;
&lt; to <
&gt; to >