Thanks for your response. A hash approach would be great, but not sure how to make the substituions. The actual 'OriginalNames.txt' would contain the names one after another such as:

Earth

Jupiter

Venus

Mars

The 'AlternateNames.txt' file would contain the exact replacement in the same order aligning to the 'OriginalNames.txt such as:

Host1

Host2

Host3

Host4

Thus, Earth would be replaced by Host1, Jupiter replaced by Host2, Venus Replaced by Host3 and Mars replaced by Host4