Here is a code in Mathematica I started to develop for a recent code golf.
It is a minimal matching, non greedy, recursive algorithm. That means that the sentence "the pen is mighter than the sword" (without spaces) returns {"the pen is might er than the sword} :)
findAll[s_] :=
Module[{a = s, b = "", c, sy = "="},
While[
StringLength[a] != 0,
j = "";
While[(c = findFirst[a]) == {} && StringLength[a] != 0,
j = j <> StringTake[a, 1];
sy = "~";
a = StringDrop[a, 1];
];
b = b <> " " <> j ;
If[c != {},
b = b <> " " <> c[[1]];
a = StringDrop[a, StringLength[c[[1]]]];
];
];
Return[{StringTrim[StringReplace[b, " " -> " "]], sy}];
]
findFirst[s_] :=
If[s != "" && (c = DictionaryLookup[s]) == {},
findFirst[StringDrop[s, -1]], Return[c]];
Sample Input
ss = {"twodreamstop",
"onebackstop",
"butterfingers",
"dependentrelationship",
"payperiodmatchcode",
"labordistributioncodedesc",
"benefitcalcrulecodedesc",
"psaddresstype",
"ageconrolnoticeperiod",
"month05",
"as_benefits",
"fname"}
Output
twodreamstop = two dreams top
onebackstop = one backstop
butterfingers = butterfingers
dependentrelationship = dependent relationship
payperiodmatchcode = pay period match code
labordistributioncodedesc ~ labor distribution coded es c
benefitcalcrulecodedesc ~ benefit c a lc rule coded es c
psaddresstype ~ p sad dress type
ageconrolnoticeperiod ~ age con rol notice period
month05 ~ month 05
as_benefits ~ as _ benefits
fname ~ f name
HTH