Depending upon what format your source text is in, Python can also make short work of such a problem. If you can import the text into a python string (or list of strings), or even paste it into a Construct EditBox object, you can do something like this:
[code:2l3t03l5]text = "one plus one equals two, and four minus three equals one."
terms = [['three', 'five'],
for find, repl in terms:
text = text.replace(find, repl)
...which results in this:
[code:2l3t03l5]two plus two equals four, and seven minus five equals two.[/code:2l3t03l5]
There are some pretty powerful string methods built-in to Python
. You can even do this in Construct.