Re: draw a graph

[psini]

If the page returns with a server error (5xx) you should check the web server log to see what happened.

In this case, my best guess is that the server has not permissions to open graph.png for output; in general it is a bad idea using a relative path in a cgi script, for you really don't know which the current dir is at execution time. Try again, specifying an absolute patch name in your open, and a path in which the user running the web server has permission to write into.

[AnomalousMonk]

... my best guess is that the server has not permissions to open graph.png for output ...

It's also a good idea to let yourself know about such problems as they develop. Something along these lines might be informative:

my $filename = 'graph.png';
open my $fh, '>', $filename or die "opening $filename: $!";
binmode $fh;
print $fh $mygraph->plot(\@data)->png or die "writing $filename: $!";
close $fh or die "closing $filename: $!";

[Bloodnok]

Indeed ... even better would be to use CGI::Carp; to allow the errors &/or warnings to be seen by/in the browser, otherwise they'll only ever be seen in the server logs - but this may be a/the requirement.