A quick try:

my $string = join \000, @code;
$string =~ s!("\w+")!<b>$1</b>!g;
@newcode = split /\000/, $string;
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See perlre. The regex should be executed each time in the loop BTW. Are you sure that not all the text is in one item for some reason? Try the g modifier after your regex, see if that cures it.

I also changed the regex a bit. See 7 Stages of Regex Users and Death to Dot Star!. Depending on the complexity of your input, you might be better of with Parse::RecDescent or siblings.

Jeroen
"We are not alone"(FZ)