i would probably go with what the other monks suggested, but here's something simple as well. I'll assume that your text file is just that, a simple text file with line returns.
to output it, try this:
print "Content-type: text/html\n\n";
note the 'pre' tags in there. \n's at the end of lines are actually processed within those so your text file will output the way you want it to :).