CGI programs can be debugged by using the ptkdb debugger in the X-windows environment. Execute xhost + on the machine where the debugger is to be displayed. This allows the web server to open the window on the machine where the ptkdb window is to be displayed.

This technique is complimentary to the more common techniques of sending the error messages to the browser, examining the error logs, and diagnostic print statements. 

#!/usr/bin/perl -d:ptkdb
 
BEGIN {
  # Set the DISPLAY variable to the name of the local machine
  # where the debugger window and web browser appear.
  $ENV{DISPLAY} = "mymachine:0" ;
}
 
print "Content-type: text/html\n\n";
print "<PRE>";
for (my $i=0; $i<10; $i++)
{
  print "Count $i\n";
}
print "</PRE>\n";

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