HTMLエスケープ
HTML::Entitiesを使うと簡単です。
use strict;
use warnings;
use HTML::Entities;
my $data = '<span id="item">data</span>';
my $safe = encode_entities($data, q{&<>"'});
my $text = decode_entities($data, q{&<>"'});
print $safe, "\n";
print $text, "\n";
