Wednesday, January 31st, 2007
perl -ple "y/[a-m][n-z][A-M][N-Z]/[n-z][a-m][N-Z][A-M]/"
Just pipe whatever you want to Rot13 into it. For best results: Print, Pipe, and Repeat.
Update: Shorter by two characters, and a bit clearer:
perl -ple "y/[a-m,A-M][n-z,N-Z]/[n-z,N-Z][a-m,A-M]/"
Update 2: Peter suggested this, and I don’t know why I didn’t think of it myself. Four characters shorter:
perl -ple "y/[a-mA-M][n-zN-Z]/[n-zN-Z][a-mA-M]/"