#! /usr/bin/perl

# not_vs_! illustrates the difference in effect caused by operator precedence

use strict;
use warnings;

explore (' if  (not $foo  &&  $bar ne "")  {1;} ',
	 ' if ((not $foo) && ($bar ne "")) {1;} ');

explore (' if  (! $foo  &&  $bar ne "")  {1;} ',
	 ' if ((! $foo) && ($bar ne "")) {1;} ');

sub explore {
   
    foreach my $expr (@_) {
        print "\nExpression $expr\n";
        print "foo bar !foo  bnn result \n";
        foreach my $foo (0, 1) {
    	    my $nfu	= (not $foo);
            foreach my  $bar ("", 1) {
    	        my $bnn     = ($bar ne "");
    	        my $result  = eval "$expr";
    	        printf "%2s%4s%5s%5s%4s\n",$foo, $bar, $nfu, $bnn, $result ;
    	    }
        }
    }
}
# not_vs_! Ends