Hi there. I was looking for a solution to a similar problem earlier today - complicated by the fact that a string might already have entities in it, but might not. (XML files passed in by external content suppliers - ugh!)

I eventually built a solution around regexes, that I thought I'd share in case any body else finds it useful.

It should be easy to customise by altering just the first two lines - the first is the text to get replaced, the second the text to replace it with.

#NOTE: the first entry here is an extended regex that says, match an &
+ that is NOT followed by between 2 and 4 word characters and a semico
+lon.
#This should prevent it from double-encoding entites that already exis
+t and hence corrupting the XML.

my @entities_bare=qw/&(?!\w{2,4};) " ' < >/;
my @entities_encoded=qw/&amp; &quot; &apos; &lt; &gt;/;

sub encode_entities {
    my $string=shift;
    
    #print "trace: in encode_entities\n";
    for(my $n=0;$n<scalar @entities_bare;++$n){
        #print "encode_entities: searching for ".$entities_bare[$n]." 
+to replace with ".$entities_encoded[$n]."...\n";
    
        if(not $string=~s/$entities_bare[$n]/$entities_encoded[$n]/g){
            #print "encode_entities: WARNING: found no entites for ".$
+entities_bare[$n].".\n";
        }
    }
    return $string;
}
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