...
 my $input = <STDIN>;
 chomp $input;

 my $regex;
 $regex = transform_string_to_optimal_matching_regex($input);

 if( $input =~ /$regex/ ) {
   print "regex |$regex| to input |$input| mapping succeeded\n";
 } 
 ...

##</code><code>##

sub transform_string_to_optimal_matching_regex {
 my $given_string = shift;
 my $regex = '';
 my $optimal_solution_found = 0;
 
 while(! $optimal_solution_found ) {
    #
    # construct optimal regex by some
    # stochastic algorithm, possibly
    # long running Monte Carlo-solver
    #
 }
  return $regex;   
}