Syntax
 aString unlike "regExpPattern";
SemanticsReturns true if regExpPattern does not match aString, otherwise false. It is equivalent to not like.
Substitutables"regExpPattern"Can be a literal like "abc" or any other regular expression . Regular Expressions provides an overview of regular expression syntax. "regExpPattern" must be enclosed in double quotes. An introduction into regular expressions can be found at http://www.regular-expressions.info/. 
Examples

The example below assigns the boolean result of the relational expression with unlike operator to variable b1. The expression evaluates to true if the string s1 is not "abc".

set b1 = s1 unlike "abc";

The example below assigns the boolean result of the relational expression with unlike operator to variable b2. The expression evaluates to true if the string s2 does not contain at least one letter or only lower case letters.

set b2 = s2 unlike "[a-z]+";

Example File (Builder project E2E Action Language/BaseTypes):

<your example path>\E2E Action Language\BaseTypes\uml\boolean.xml