How to generate a base64 encoding of a string

eg. to encode the word "username"

perl -MMIME::Base64 -e 'print encode_base64("username");'

Note:
-M is the switch for specifying the module to use
MIME::Base64 is the module

perl syntax:

Usage: perl [switches] [--] [programfile] [arguments] -0[octal] specify record separator (replacebegin:content:replaceend, if no argument) -a autosplit mode with -n or -p (splits $_ into @F) -C[number/list] enables the listed Unicode features -c check syntax only (runs BEGIN and CHECK blocks) -d[:debugger] run program under debugger -D[number/list] set debugging flags (argument is a bit mask or alphabets) -e program one line of program (several -e's allowed, omit programfile) -E program like -e, but enables all optional features -f don't do $sitelib/sitecustomize.pl at startup -F/pattern/ split() pattern for -a switch (//'s are optional) -i[extension] edit <> files in place (makes backup if extension supplied) -Idirectory specify @INC/#include directory (several -I's allowed) -l[octal] enable line ending processing, specifies line terminator -[mM][-]module execute "use/no module..." before executing program -n assume "while (<>) { ... }" loop around program -p assume loop like -n but print line also, like sed -s enable rudimentary parsing for switches after programfile -S look for programfile using PATH environment variable -t enable tainting warnings -T enable tainting checks -u dump core after parsing program -U allow unsafe operations -v print version, patchlevel and license -V[:variable] print configuration summary (or a single Config.pm variable) -w enable many useful warnings -W enable all warnings -x[directory] ignore text before #!perl line (optionally cd to directory) -X disable all warnings