Source
"I am not a number! I am a free man!"

Prefix           Suffix 
"" ""            "I"
"" "I"           "am"
"I" "am"         "a"
"I" "am"         "not"
"a" "free"       "man!"
"am" "a"         "free"
"am" "not"       "a"
"a" "number!"    "I"
"number!" "I"    "am"
"not" "a"        "number!"

Generated sentences beginning with the prefix "I am"
"I am a free man!"
"I am not a number! I am a free man!"
"I am not a number! I am not a number! I am a free man!"
"I am not a number! I am not a number! I am not a number! I am a free man!"