Hi, I have 2 files, one INDEX which has a list of line numbers, one at a line for example 
1145
3453
4534
345
3
456
.
.
.

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The second file contains data. I am wondering whats the best way to write a perl script which replaces "foo" with "bar" on the line numbers mentioned in the index file? The method I currently thought up will be CPU intensive, i.e. parsing the data file multiple times. For example if index as 100 entries, I will parse the data file 100 times. Big data file means inefficient processing. I think using sort, and some kind of partial processing will help here better?

In reply to Replacing expression on certain line numbers by tsk1979

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