my %subst = (
       q|&| => q|&|,
       q|"| => q|"|,
       q|<| => q|&lt;|,
       q|>| => q|&gt;|,
       q|'| => q|&'|,
       q|`| => q|&`|,    
   );
   
$$data =~ s/($_)/$subst{$1}/sg foreach keys %subst;