#from Anonymous Monk code
> my %allowed = qw{ ( ( ) ) ! !! & &&  };
> my $finalExpr = map { $allowed{$_} || die "not allowed '$_'" } split '', $expr;

##</code><code>##

 print "EXPR = ",$newExpr,"\n";

 # don't know how to execute shell commands without [A-Za-z] letters
 $newExpr =~ /^([\d\s()&|!]+)$/;
 printf "%b\n", eval $1;
}