Index: utils/extract_vplan.py
===================================================================
--- /dev/null
+++ utils/extract_vplan.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+# This script extracts the VPlan digraphs from the vectoriser debug messages
+# and saves them in individual dot files (one for each plan). Optionally, and
+# providing 'dot' is installed, it can also render the dot into a PNG file.
+
+import sys
+import re
+import argparse
+import shutil
+import subprocess
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--png', action='store_true')
+args = parser.parse_args()
+
+dot = shutil.which('dot')
+if args.png and not dot:
+    raise RuntimeError("Can't export to PNG without 'dot' in the system")
+
+pattern = re.compile(r"(digraph VPlan {.*?\n})",re.DOTALL)
+matches = re.findall(pattern, sys.stdin.read())
+
+for vplan in matches:
+    m = re.search("graph \[.+(VF=.+,UF.+), ", vplan)
+    if not m:
+        raise ValueError("Can't get the right VPlan name")
+    name = re.sub('[^a-zA-Z0-9]', '', m.group(1))
+
+    if args.png:
+        filename = 'VPlan' + name + '.png'
+        print("Exporting " + name + " to PNG via dot: " + filename)
+        p = subprocess.Popen([dot, '-Tpng', '-o', filename], encoding='utf-8',
+                              stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        out, err = p.communicate(input=vplan)
+        if err:
+            raise RuntimeError("Error running dot: " + err)
+
+    else:
+        filename = 'VPlan' + name + '.dot'
+        print("No visualisation requested, saving to file: " + filename)
+        with open(filename, 'w') as out:
+            out.write(vplan)