## Ruby, <s>25</s> <s>24</s> <s>23</s> 18 bytes <!-- language-all: lang-ruby --> p /\D0|^..$/!~gets [Try it online!](https://tio.run/nexus/ruby#fU27DsIwDNzzFUZidFMHilR2/sKYqRFi4CG1I@LXw7ltGIniy/li35XUxel2zyMNz0D0ovZ8kvclxm27@VzzNIb8GErRZEGTANQcFILNzJjAHZh2s1I7RVsZar8u9C72qKP9mI/J8o/rMcLUeGaDdVkS1wG8Nc1dmTqmw19nd8D5Ag "Ruby – TIO Nexus") This is a full program that takes input in Ruby's canonical array format on STDIN and outputs `true` or `false` on STDOUT. gets # read line of input / /!~ # does not match the regex... \D0 # a non-digit followed by a 0 | # or... ^..$ # a 2-length string (which must be [], the empty array) p # output the result **23 byte** function version: ->a{"#{a}"!~/\D0|^..$/} This is a proc that takes one argument, the array to be tested. Thanks to [Martin Ender](http://codegolf.stackexchange.com/users/8478/martin-ender) for a byte!