Thank you! I fixed that and now have

#!/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"
--
[download]

I'm still getting Server error! The server encountered an internal error and was unable to complete your request. Error message: Premature end of script headers: test6.pl

Any other suggestions?