Base64 is used to encode binary data in printable ASCII form. de64 is a trivial perl script to decode such strings:

use MIME::Base64;
local $/ = undef;
print decode_base64(shift||<STDIN>);

One application of de64 is decoding UTF8 LDAP attributes inside LDIF files. For instance, “cn:: Um9iZXJ0byBNYXJ0w61uZXo=” may be decoded with

$ de64 Um9iZXJ0byBNYXJ0w61uZXo=
Roberto Martí­nez

(Look Randal! I’m using a CPAN module this time! ;-) ) Of course, all the heavy lifting is done by MIME::Base64 from CPAN.