Question : What do I do about those exclamation points and unwanted line breaks?

I'm using MIME::Lite and XML::Twig to allow users to send email attachments that contain the contents of db searches they've performed. In the email form, the users can select HTML or Plain text as the format for the attachment. There are no problems with the HTML attachment, but with the plain text attachment, paragraphs that have more than about 989 characters are broken up  with a line break and an exclamation point like so:

Published abstract:
BACKGROUND: Irbesartan has been shown to reduce the doubling of serum creatinine (a strong predictor of progression to end-stage renal disease), the onset of end-stage renal disease and all-cause mortality in patients with type 2 diabetes when compared with standard care and amlodipine. OBJECTIVE: The present study assessed the cost effectiveness of irbesartan, an angiotensin II receptor antagonist, and amlodipine, a calcium channel blocker, in the treatment of Canadian patients with diabetic nephropathy and hypertension. METHODS: The analysis was conducted based on a Markov model using Monte Carlo simulation analysis to estimate the expected values for outcomes of interest. Transition probabilities were obtained from a comparative trial of amlodipine, irbesartan and standard care (antihypertensive treatment excluding other angiotensin II receptor antagonists or calcium channel blockers) in patients with overt diabetic nephropathy and hypertension. Canadian costs for the hea!
 lth states studied were obtained from published data. RESULTS: Based on the results of the Monte Carlo simulation, irbesartan was dominant over standard care and amlodipine because it both reduces costs and leads to greater life expectancy. The incremental cost-effectiveness ratio for amlodipine in comparison with standard care was $102,000. Estimates of net benefit were correlated with transition probabilities relating to progression from the initial health state. The results were insensitive to univariate sensitivity analysis. CONCLUSIONS: Irbesartan use would lead to a reduction in medical costs and an increase in life expectancy when compared with amlodipine or standard care.

Why is this happening and how do I fix it?

Here's some of the code. If more details are necessary, I can provide them.

the part that gets the abstract...

      }

     if ( $abst_txt ) {
       print "\nPublished abstract:\n";
       print $abst_txt;
        };
     if ((!$abst_txt) && (!$sdiSum_txt)) {
       print "\nPublished abstract:\nNot available.";
        };
     if ( $sdiSum_txt ) {
       print "\nSDI summary:\n";
       print $sdiSum_txt . $prodNM_txtB
        };

     print "";
     }

Thanks!

Answer : What do I do about those exclamation points and unwanted line breaks?

Did you read the comments about MIME::QuotedPrint in that other question I referred you to? This format should be accepted by most mail clients and they should reconstitute your original file, complete with very long lines, from the mail message.