1. First, you need to replace "\w\d+" with "\w+\d+". Otherwise, your regex is only going to match "x1.data" instead of "xxx1.data".
  2. Second, I assume you're using bash, sh, or a similar shell on a Unix box. When passing arguments using double-quotation marks, you need to escape any backslashes, dollar signs, and certain other characters. I recommend using single-quotation marks instead since most characters don't have to be escaped inside them.

Suggestion:

perl -npi.bak -e 's:(\w+\d+\.data):testname/$1:g' file1.txt

In reply to Re^3: how to modify the text in file by dse
in thread ho w to replace a occurence of string by other string by Anonymous Monk

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