How about delayed execution? You push all commands onto a stack and only execute after reading all data: 

sub story {
    my ($source,$author) = @_;
    my $tab = 3;
    
    my @toc;
    my @commands;
    push @commands, [ \&startsection, "Lead" ];
    
    # I ran $source above, so I can't have it here! /me head desks.
    while (my $line = <$source>) {
        chomp($line);
        
        # If a line starts with a bracket, just print the line.
        if ($line =~ m/^</) {
            push @commands, [ \&line, $tab, $line ];
        }
        
        # If a line starts with a numeral 1-6, print a heading.
        elsif ($line =~ /^[1-6]\s/) {
            my ($heading,$text) = split(/ /,$line,2);
            if( $heading == 2 ) {
                push @toc, anchor($text, { href => '#'.idify($text) } 
+);
                if( $commands[-1]->[0] eq \&startsection ) { # not sur
+e this comparison is valid...
                    pop @commands; # to avoid empty sections
                } else {
                    push @commands, [ \&endsection ];
                }
                push @commands, [ \&startsection, $text ]; # adapt arg
+uments as required
            }
            my $id = idify($text);
            push @commands, [ \&heading, $tab,$heading,$text, { id => 
+$id } ];
        }
        
        # If a line is a break or horizontal rule, print the line in b
+rackets.
        elsif ($line =~ /^[bh]r$/) {
            push @commands, [ \&line, $tab, "<$line>" ];
        }
        
        # All other lines are paragraphs.
        else {
            push @commands, [ \&paragraph, $tab, $line  ];
        }
    }
    push @commands, [ \&endsection ];    

    # do the table of contents
    list($tab, 'u', \@toc, { class => 'two' });

    # delayed execution of all print commands
    for (@commands) {
        my $cmd = shift @$_;
        $cmd->(@$_);
    }

    # If I wrote a story, I want people to know I wrote it at the bott
+om.
    paragraph($tab,"written by $root_user", { class => 'author' }) if 
+!$author;
}

[download]

I cannot test this code but it hopefully conveys the idea...

startsection and endsection would be two subs to print the HTML to start and end a section.

Update: some changes in formatting of the post and added a missing comma in the code.

Update: added a missing endsection at the end.

In reply to Re^3: Group __DATA__ lines in a while? by hdb
in thread Group __DATA__ lines in a while? by Lady_Aleena

Title:
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