Some reading that might make this behavior more clear is Scalar values from perldata.

In order to have its ability to silently work with strings, numbers and booleans without explicit coding of intent, Perl actually stores appropriate values internally. When you use the expression $var = !$var;, you set the variable to FALSE and clear out any numbers or strings associated with it. When you then ask it to print $var, Perl checks what it knows about the value. Since you want a string and the value is FALSE, it outputs "", the false string. Hence, after toggling, you actually have @array = ('1', '', '1'); You can get your expected behavior if you numify, for example with the code $_ += 0 foreach @array;. This will tell Perl to store a numerical value, which it will check before output.

As a side note, you should pick visible characters as delimiters when checking what you are actually outputting. If you'd used print "<$_>"; for example, you would have gotten the much more obvious <1><><1> as output.

Thanks for a very clear explanation and advice about the log..I think its is a profound concept for a beginner..I am glad I asked

What is true and false in Perl?, Tutorial::What is true and false?, True or False? A Quick Reference Guide

Why do you expect zero specifically?

The false value typically returned by Perl is a special value that's "" when treated as a string and 0 when treated as a number.

$ perl -wle'my $x = !1; print "".$x; print 0+$x;'

0

$ perl -wle'my $x = ""; print "".$x; print 0+$x;'

Argument "" isn't numeric in addition (+) at -e line 1.
0

$ perl -wle'my $x = 0; print "".$x; print 0+$x;'
0
0
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I am using it check the results later in the code..but thanks guys!!

You apparently have a boolean, so checking involes using

if (!$value)
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instead of

if ($value == 0)
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Mind you, the latter would work fine with !1 as well, so I don't see the problem.

If need to format it to print it, you can use the conditional operator.

print("value = ", $value?"true":"false", "\n");
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But there's no need to format it until it's time to output it.

@array = (0, 1, 0);
@array = map {1 - $_} @array;
say "@array";   # 1 0 1
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use strict;
use warnings;
use Data::Dumper;

my @array = (1,0,1);

for my $item (@array) {
    $item = !$item + 0;
}

print Dumper(\@array);
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Update: or even shorter, but perhaps less legible:

$_=!$_+0 for @array;
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Not sure why you have three outputs on the first line and only two on the second, but nevermind.   Just use $array[$i] = ($array[$i] ? 0 : 1);

This is the sort of “problem” that just is not worth pulling out hair over.   “Don’t bother to ask Why.   Just write Something That Works, and that is reasonably clear to you and to your successor, and move along.”

Thats the output..its not printing anything when i try to print !1, but ya..I think the james2vegas's explanation that 1 is negating to " " makes sense...Thanks for replying

O => 1; 1 => 0 is the truth table for exclusive disjunction; ie. XOR:

print @a;;
1 1 0 0 1 1 0 0 0 0 0 1 1 1 0 0 

$_ ^= 1 for @a;;

print @a;;
0 0 1 1 0 0 1 1 1 1 1 0 0 0 1 1
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This is working for me it does not use Boolean values.

#!/usr/bin/perl
#
use strict;
use warnings;
while (<DATA>) { print;
chomp;
foreach (split /,/){print $_ ? "0," :  "1,";}
print "\n";
}
__DATA__
0,1,1
1,1,0
0,1,0
1,0,0
1,1,1
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use strict;
use warnings;

my @foo = (0, 1, 0);
print " \@foo: @foo\n";

$_ = !$_?1:0 for @foo;
print "!\@foo: @foo\n";
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Just for completeness: the following node lists a lot of additional ways of toggeling between 0 and 1: Boolean counter?