import re    
lines = ['SITE start', 'SITE1 more', 'SITE2 end','INS value1', 'INS 1 value2']
headings = ['SITE','SITE1',"SITE2", r"INS(?! \d)", "INS 1"]
headings=sorted(headings, key=lambda x: len(x), reverse=True)
for line in lines:
    print("----")
    for heading in headings:
        headregex = r"\b{}\b".format(heading)
        match = re.search(headregex,heading)
        if match:
            print "Found " + heading + " " + line
        else:
            print "Not Found " + heading + " " + line

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