[Gnuplot-py-users] multiplot but in the same graph

is there any way to introduce a line with a concrete character while creating 
a file, so that I can plot every piece of file between those characters as an 
individual plot, once above the others?? I mean... I want to save in a file 
several points, of several people. Then I want to compare all those people in 
a graph, so I want to plot each person's respective points in a different 
color and so on.  
Thank you very much if you can help me.