Re: What is the correct definition of False and Null in Perl? (OT: Formatting of OP)

[ww]

It would be nice if the code your next post is self-consistent and reasonably indented. Did someone suggest that you get bonus points for using fewer lines and less white space? If so, whack that someone for giving you a bum steer... and make your next post readily readable. It'll help you get answers.

Also, consider your output: labeling make it easier to read and understand. Your tabs in the lines with which you disagreed was a big step in the right direction but consider how labeling makes the way you wrote your $var...s easier to know, from the output alone.

Something like this may serve as an example:

#!/usr/bin/perl
use strict;
use warnings;
# 930247


my $var = 0;   
if ( $var ) {
    print "\$var ($var) True\n"; 
} else {
    print "\$var ($var) False\n"; }

undef $var;    
if ( $var ) {
    print "\$var (undef) True\n"; 
} else {
    print "\$var (undef) False\n"; 
}

my $var1 = '';
if ( $var1 ) {
    print "\$var1 ('') True\n"; 
} else {
    print "\$var1 ('')  False\n"; 
}

my $var2 = "";  
if ( $var2 ) {
    print "\$var2 (\"\")  True\n"; 
} else {
    print "\$var2 (\"\")  False\n"; 
}

my $var3 = '0'; 
if ( $var3 ) {
    print "\t \$var3 ($var3 - as a single-quoted number) True\n"; 
} else {
    print "\t \$var3 ($var3 - as a single-quoted number) False\n"; 
}
my $var4 = "0"; 
if ( $var4 ) {
    print "\t \$var4 ($var4 - as a double-quoted number) True\n"; 
} else {
    print "\t \$var4\ ($var4 - as a double-quoted number) False\n"; 
}

if ( $var4 == 0 ) {
    print "\t \$var4  ($var4  - as an unquoted number) True\n"; 
} else {
    print "\t \$var4  ($var4 - as an unquoted number) False\n"; 
}

if ( $var4 eq '0' ) {
    print "\t \$var4  ($var4 - as a single-quoted number) True\n"; 
} else {
    print "\t \$var4  ($var4 - as a single-quoted number) False\n"; 
}
print "\t \$var4  ($var4 - as a single-quoted number) has length of " 
+. length($var4) . " and ASCII value of " .ord($var4). "\n";

my $var5 = '1'; 
if ( $var5 ) {
    print "\$var5 ($var5 in single quotes) True\n"; 
} else {
    print "\$var5 ($var5 in single quotes) False\n"; }

my $var6 = "1"; 
if ( $var6 ) {
    print "\$var6 ($var6 in double quotes) True\n"; 
} else {
    print "\$var6 ($var6 in double quotes) False\n"; 
}
my $var7 = 1;   
if ( $var7 ) {
    print "\$var7 ($var7 - as an unquoted number) True\n"; 
} else {
    print "$var7 ($var7 - as an unquoted number) False\n"; 
}

and that produces this output:

$var (0) False
$var (undef) False
$var1 ('')  False
$var2 ("")  False
         $var3 (0 - as a single-quoted number) False
         $var4 (0 - as a double-quoted number) False
         $var4  (0  - as an unquoted number) True
         $var4  (0 - as a single-quoted number) True
         $var4  (0 - as a single-quoted number) has length of 1 and AS
+CII value of 48
$var5 (1 in single quotes) True
$var6 (1 in double quotes) True
$var7 (1 - as an unquoted number) True

You'll also note an (imperfect) effort to do the quoting for output in the same manner each time; that kind of consistency will also help make your code more understandable... and maintainable.

But most inportant -- make sure you grok davidos reply; hold it close until it's second nature. That will save more important problems, later.