It relies on the characteristic of a given n-variable Boolean formula in conjunctive normal form, which is known as satisfiability, and Cook's theorem indicates satisfiability has this property.  
The regular pattern expression matching function in Perl bears this property.  It relies on the characteristic of a given n-variable Boolean formula in conjunctive normal form, which is known as satisfiability, and Cook's theorem indicates satisfiability has this property.  Formally, it is defined in terms of reduction, the idea that if problem A is easier to solve than B, a relationship can be drawn between the two that defines this property for B.  FTP, identify this property known to have no polynomial time solutions, famously including the traveling salesman problem.
The regular pattern expression matching function in Perl bears this property.  
NP-completeness