As you might expect, this has been golfed a few times before. For example:

The Qwika Perl wikipedia example program (which matches Anony's response above) is: 
perl -pe 'tr/A-Za-z/N-ZA-Mn-za-m/' < input_file > output_file

[download]
while the shortest Perl solution at shinh's golf site is: 
#!perl -p
y/N-ZA-z/A-za-m/

[download]

In reply to Re: Rot13 Challenge by eyepopslikeamosquito
in thread Rot13 Challenge by PyrexKidd

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