Hi Aleena,

No idea if this is cookie worthy, but you got me interested in looking at the Text::Balanced module:

use Text::Balanced qw(extract_multiple gen_extract_tagged);

my $codes = qr(A|ABBR|ACRONYM|B|BIG|CITE|CODE|DFN|EM|I|KBD|SAMP|SMALL|
+SPAN|STRONG|SUB|SUP|TT|VAR);
my $extractor = [
        gen_extract_tagged('<!--', '-->', ''),
        gen_extract_tagged("$codes<", '>', '')
];

# Join all plain text segments, and element substitutions; removing co
+mments
sub inline {
        my $text = shift;
        my $result = '';
        for (extract_multiple $text, $extractor) {
                $_ = element(lc $1,$2) if /^($codes)<(.*)>$/;
                $result .= $_ unless (/^<!--/);
        }
        return $result;
}

# Handle a tag element with attribute if one exists, and then recurse 
+into it
sub element {
        my ($id,$inner) = @_;
        return  ($inner =~ s/\|([^<>]+?)$// ? "<$id $1>" : "<$id>") .
                inline($inner) .
                "</$id>";
}

print inline
   'Anyone who watches the Syfy channel knows that on Monday nights ' 
+.
   'they aired three television series I<A<EurSUP<e>ka|href=' .
   '"Movies_by_series.pl?series=EWA#EUReKA">|class="title">, I<A<Wareh
+ouse ' .
   '13|href="Movies_by_series.pl?series=EWA#Warehouse_13">>, and I<A<A
+lphas' .
   '|href="Movies_by_series.pl?series=EWA#Alphas">>. Some might not be
+ aware ' .
   'that these three series have formed a crossover cosmology which I 
+call A<' .
   'EWA|href="Movies_by_series.pl?series=EWA"><!-- This is a long stri
+ng. -->';
[download]

Which prints the same output as in your example using Perl 5.8.8. The key is using extract_tagged which will match your codes exactly. For instance this is the results of the first extract_multiple :

'Anyone who watches the Syfy channel knows that on Monday nights they 
+aired three television series '
'I<A<EurSUP<e>ka|href="Movies_by_series.pl?series=EWA#EUReKA">|class="
+title">'
', '
'I<A<Warehouse 13|href="Movies_by_series.pl?series=EWA#Warehouse_13">>
+'
', and '
'I<A<Alphas|href="Movies_by_series.pl?series=EWA#Alphas">>'
'. Some might not be aware that these three series have formed a cross
+over cosmology which I call '
'A<EWA|href="Movies_by_series.pl?series=EWA">'
'<!-- This is a long string. -->'
[download]

Everything is already broken up nicely and all that is left to do is recurse inside the tags found to handle any nested codes.

This does nothing more than your code however, as usual just TIMTOWTDI.

OK, this took me a lot longer than I expected it to, and the algorithm ended up a little convoluted, but I think this better handles a few edge cases...

use v5.14;
use strictures;

package Parser {
    use Moo 1.006000;
    use Types::Standard qw( RegexpRef ArrayRef );
    use Text::Balanced qw( extract_bracketed );
    use HTML::Entities qw( encode_entities );
    use namespace::autoclean;
    
    my $Allowance = RegexpRef->plus_coercions(
        ArrayRef, sub { qr/${\( join "|", map quotemeta, @$_ )}/ },
    );
    
    has allowed_tags => (
        is       => 'ro',
        isa      => $Allowance,
        coerce   => 1,
        builder  => sub {
            [qw(A ABBR ACRONYM B BIG CITE CODE DFN EM I KBD Q SAMP
            SMALL SPAN STRONG SUB SUP TT VAR)]
        },
    );
    
    sub print {
        my $self = shift;
        $self = $self->new unless ref $self;
        print $self->parse($_) for @_;
    }
    
    sub parse
    {
        my $self = shift;
        my ($text) = @_;
        
        my $tags = $self->allowed_tags;
        
        my ($before, $match) = ($text =~ m{
            \A             # start of string
            (.*?)          # leading text ($before)
            (              # either...
                \<\!--      #    the start of a comment
                |           # or...
                $tags\<     #    a tag
            )
        }xsm) or do {
            my @return = split /\|/, $text;
            $return[0] = encode_entities($return[0]);
            return @return;
        };
        
        # strip $before from $text
        substr($text, 0, length($before)) = '';
        
        # If the first thing that needed to be handled was a comment
        if ($match eq '<!--') {
            # Strip it out
            $text =~ s/\<\!--(.+?)--\>//g;
            
            # Handle the rest via recursion
            return join "", $before, $self->parse($text);
        }
                
        chop(my $found_tag = lc $match);
        substr($text, 0, length($found_tag)) = '';
        my ($got, $remainder) = extract_bracketed($text, q/<"'>/);
        $got = substr($got, 1, length($got) - 2);
        my ($markup, @attrs) = $self->parse($got);
        my ($more_markup, @more_attrs) = $self->parse($remainder);
        $_ //= '' for $markup, $more_markup;
        
        join("",
            $before,
            (@attrs ? "<$found_tag @attrs>" : "<$found_tag>"),
            $markup,
            "</$found_tag>",
            $more_markup,
        ), @more_attrs;
    }
}

Parser->print(<<'TEXT');
Anyone who watches the Syfy channel knows that on
Monday nights they aired three television series
I<A<EurSUP<e>ka|href="Movies_by_series.pl?series=EWA#EUReKA">|class="t
+itle">,
I<A<Warehouse & 13|href="Movies_by_series.pl?series=EWA#Warehouse_13">
+>,
and I<A<Alphas|href="Movies_by_series.pl?series=EWA#Alphas">>.
Some might not be aware that these three series have formed a crossove
+r
cosmology which I call A<EWA|href="Movies_by_series.pl?series=EWA">
<!-- This is a long string. -->
TEXT
[download]

Hello tobyink. Thank you for taking the time to write this, however I don't understand it and would not be able to maintain it. You used objects which completely confuse me. Also, you used Perl 5.14 instead of 5.8.8, so it may not work on my web host. I hadn't heard of strictures until now. I think you encoded the entities prematurely (only encode the text within the tags). I'm not sure why autoclean is needed, or why you needed Types::Standard. Could this be rewritten in a purely functional way, or are objects required to make this work? I don't see a function called inline to return the parsed text (the text is printed later) or a way to create it.

I'm sorry I can't make use of this, would cookies help?

No matter how hysterical I get, my problems are not time sensitive. So, relax, have a cookie, and a very nice day!
Lady Aleena

It's easy enough to change it to a single function...

use strict;
use warnings;

use Text::Balanced qw( extract_bracketed );
use HTML::Entities qw( encode_entities );

my $default_allowed_tags = do {
    my @tags = qw(
        A ABBR ACRONYM B BIG CITE CODE DFN EM I KBD Q SAMP
        SMALL SPAN STRONG SUB SUP TT VAR
    );
    qr/${\( join "|", map quotemeta, @tags )}/;
};

sub parse_markup
{
    my ($text, $tags) = @_;
    $tags ||= $default_allowed_tags;
    
    my ($before, $match) = ($text =~ m{
        \A             # start of string
        (.*?)          # leading text ($before)
        (              # either...
            \<\!--      #    the start of a comment
            |           # or...
            $tags\<     #    a tag
        )
    }xsm) or do {
        my @return = split /\|/, $text;
        $return[0] = encode_entities($return[0]);
        return @return;
    };
    
    # strip $before from $text
    substr($text, 0, length($before)) = '';
    
    # If the first thing that needed to be handled was a comment
    if ($match eq '<!--') {
        # Strip it out
        $text =~ s/\<\!--(.+?)--\>//g;
        
        # Handle the rest via recursion
        return join "", $before, parse_markup($text, $tags);
    }
            
    chop(my $found_tag = lc $match);
    substr($text, 0, length($found_tag)) = '';
    my ($got, $remainder) = extract_bracketed($text, q/<"'>/);
    $got = substr($got, 1, length($got) - 2);
    my ($markup, @attrs) = parse_markup($got, $tags);
    my ($more_markup, @more_attrs) = parse_markup($remainder, $tags);
    defined($_) or $_='' for $markup, $more_markup;
    
    join("",
        $before,
        (@attrs ? "<$found_tag @attrs>" : "<$found_tag>"),
        $markup,
        "</$found_tag>",
        $more_markup,
    ), @more_attrs;
}

print for parse_markup(<<'TEXT');
Anyone who watches the Syfy channel knows that on
Monday nights they aired three television series
I<A<EurSUP<e>ka|href="Movies_by_series.pl?series=EWA#EUReKA">|class="t
+itle">,
I<A<Warehouse & 13|href="Movies_by_series.pl?series=EWA#Warehouse_13">
+>,
and I<A<Alphas|href="Movies_by_series.pl?series=EWA#Alphas">>.
Some might not be aware that these three series have formed a crossove
+r
cosmology which I call A<EWA|href="Movies_by_series.pl?series=EWA">
<!-- This is a long string. -->
TEXT
[download]

But personally I prefer the OO version because it means I can have a $parser object, which I can pass around. Code that needs to process some markup gets given the markup, and given the parser, and simply throws the markup at the parser. This makes it easy to switch in a different parser if required (say, one that generated stricter XHTML, or one that processed Markdown).

toby döt ink
c