That is graphviz rendering, so
GraphViz
Tk::GraphViz
GVEdit
also interesting
http://ditaa.sourceforge.net/ - DIagrams Through Ascii Art
http://www.jgraph.com/mxgraph.html - the AJAX diagramming solution
App::Asciio - Plain ASCII diagram

In reply to Re: GUI for building connected blocks by Anonymous Monk
in thread GUI for building connected blocks by citromatik

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