#!/usr/bin/perl -w

# test6.pl for testing real-time graph capabilities
# November 17, 2004
use CGI qw( :standard );
use CGI::Carp 'fatalsToBrowser';    #will print error message to user
my $q = new CGI;
print $q->header("image/png");
open $station => "| /usr/local/bin/gnuplot" or die "$!\n";
print $station <<"--";
set terminal png color
set output
set xdata time
set timefmt "%Y%m%d"
set key left top title "Legend" box
set grid xtics ytics
set yrange [700:]
set format x "%Y"
set xlabel "Year"
set ylabel "Sodium, water, filtered, milligrams per liter"
set title "05056670 Western Stump Lake Major Ions"
plot "05056670.txt" using 2:3 title "P00930 Sodium dissolved"
--
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Try running it from the command line to see what's going wrong, and/or check the error logs. Maybe your script doesn't have the right permissions or the path to the perl executable is wrong, or you have windows linefeeds, or any other standard CGI problem.
"What should it profit a man, if he should win a flame war, yet lose his cool?"