I am developing a module with a function that prints HTML to stdout. The function prints the standard "Content-type: text/html" before printing the HTML, assuming a CGI-like environment. The problem is that sometimes people are not using the module in a CGI script. The Content-type line shows up in the HTML and looks awkward in such cases.

So what to do? Here's one solution I came up with: 

print "Content-type: text/html\n\n" if defined $ENV{'SERVER_SOFTWARE'}
+;

[download]
But I am not sure if this is 100% foolproof. Is it?

Also, I am worried about something else: What if someone printed the header before using my function and then the header gets printed again when they use my function. The Content-type line would be printed within the HTML. How could I prevent this? Is there a way of checking if the header has already been sent?

In reply to Printing content-type in the proper context by jacques

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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