# Encoding file
perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)' < file

# Decoding file
perl -MMIME::Base64 -ne 'print decode_base64($_)' < file.b64

# HMAC-SHA1
perl -MDigest::HMAC_SHA1 -le '$_=Digest::HMAC_SHA1->new($ARGV[0])->add($ARGV[1])->b64digest; $_.="=" x length % 4; print' TestKey TestString