Note: untested.

$ perl -i.bak -lpe "s/^(N\d+ )?/$./" *.input

• The -i.bak switch says "edit the input files in place, making backup files for each with a .bak extension".
• The -l switch says "do automatic line-end processing".
• The -p switch says "iterate over each line". Well, it does a bit more than that; see perldoc:perlrun for more.
• The $. special variable holds the input line number (like NR in awk).

--
F o x t r o t U n i f o r m
Found a typo in this node? /msg me
The hell with paco, vote for Erudil!

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