# make a key file, ok for demo purposes
$ perl -e 'print chr int rand 256 for 0..10000' > key.file

# make a test source file
$ ls -al /dev > plain.txt

# encipher
$ perl cipher.pl key.file < plain.txt > cipher.txt

# decipher
$ perl cipher.pl key.file < cipher.txt > deciphered.txt

# verify
$ diff -s plain.txt deciphered.txt 
Files plain.txt and deciphered.txt are identical