perl -i~ -pe "if($ARGV ne $z){$f=$z=$ARGV;$f=~s/\.wra//;/(.{10})$/; $r
+=$1} s/$r/$f/g" *.wra
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Of course, at this point the solution stops looking elegant and cool (not that it ever really did), and there are too many one-letter variables. My recommendation is to invest some time in studying Perl and create a real script to do your modifications.

The one-liner may be cute and good for obfuscation value, but if you aren't sure what it's doing, it shouldn't go into production/be handed in for your assignment, etc. By the way, this time it's a one, not an el.

This works great! And helped me to understand how to form regular expressions. Thanks again.