#!/usr/bin/perl
# rot13it.pl

$firstfile = $ARGV[0];
$secondfile = $ARGV[1] || 
	die "rot13it - an alpha-only 13 byte-shifting substitution cypher.\n\tUsage: rot13it <infile> <outfile>\n" ;
open (FIRST, "$firstfile") || 
	die "EGADS! I can't open $firstfile\n";
open (SECOND, ">$secondfile") || 
	die "Naughty, naughty... you can't create $secondfile!\n";
while (<FIRST>){ 
$_ =~ tr/A-Ma-mN-Zn-z/N-Zn-zA-Ma-m/;
print SECOND $_;
}
close FIRST;
close SECOND;

system "ls -l $firstfile $secondfile 1>&2" ;
print STDERR "All done...bye!\n";