UPDATE: Am I imagining things or did I not see the first reply by Zaxo? Anyhow, my apologies.
Hi P0w3rK!d

On Win2k, the following one-liner may give you what you're looking for:

C:\>perl -pe "s/FOO/123/g;" in.txt
-a = fuhergrg
-b = awerh9w8eh
-c = rgiuhreg
-d = C:\tmp\123.txt
[download]

Hope this helps.

cheers, -semio