Update strings in text file

Shell Programming and Scripting
1

I have a txt file that contains multiple occurrances of:

<MoreFlag>Y</MoreFlag>

I want to update these to:

MorePACFlag>Y</MorePACFlag>

How would I do this?

Cheers
Paul

2 
perl -i -pe 's/MoreFlag>/MorePACFlag>/g' input_file
3

vim filename

vim ***
:%s/MoreFlag/MorePACFlag/g