well, strictly not related with your question, but if you have a lot of data in a text file and your goal is to produce some nice, portable and complex graphs maybe you should consider either to use any of the plethora of graph modules from cpan...

or, to pass this data to R, octave ect...You can create a lot of super-cool graphs with these programs that excel simply can't do, take a look at:

http://addictedtor.free.fr/graphiques/

You can invoke R from perl with:

use Statistics::R;
my $r_connection = Statistics::R->new();
[download]

Just another point of view. You probably don't need perl to load or import a text file to excel, you can do this directly from excel