Check the text for size. If it's over a certain limit, automatically reject the submission.

Remove all carriage returns:

$text =~ tr/\r//d;
[download]

Remove leading and trailing white space:

$text =~ s/^ +| +$//gm;
[download]

Remove any extra line breaks:

$text =~ s/^\n+|\n+$//g;
$text =~ s/\n{3,}/\n\n/g;
[download]

Then submit using placeholders to take care of potential security breaches.