As others have said, always use warings; use strict;

When you do a math operation, == or +/- etc, Perl will convert a string value to a numeric value according to its rules. Trying to use a string that does not exactly represent a number as a number causes a warning with one exception shown below.

Here is some example code:

use strict;
use warnings;
$|=1; #turn off stdout buffering so error msgs match


my $x = "awsdfasdf";
print "zero\n" if ($x==0); # zero
#Argument "awsdfasdf" isn't numeric in numeric eq (==) 
$x+= 0;
print "x\n";               #0


my $y="asdf6";   #ending digits to alpha do not count
$y+= 0;
#Argument "asdf6" isn't numeric in addition (+)
print "$y\n";   #0

my $z = "3asdf"; #beginning digits will be used
$z+=0;
#Argument "3asdf" isn't numeric in addition (+)
print "$z\n";   #3

my $x1 = "0 but true";  #more common now is 0E0
$x1+=0;                 # NO ERROR!
print "$x1\n";          #0

my $x2 = "3 camels";    #can have textual "units"
$x2+=0;
#Argument "3 camels" isn't numeric in addition (+)
print "$x2\n";         #3

__END__
Argument "awsdfasdf" isn't numeric in numeric eq (==) at line 7.
zero
x
Argument "asdf6" isn't numeric in addition (+) at line 14.
0
Argument "3asdf" isn't numeric in addition (+) at line 20.
3
0
Argument "3 camels" isn't numeric in addition (+) at line 31.
3

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As the above code shows the "0 but true" exception is hard-coded into Perl as an exception. This allows a function to return a single value that can represent both logically true and numerically zero. Using that string as a numeric value will not cause a warning. This is now seldom seen as the exponential value 0E0 is more commonly used, especially by the DBI.

In reply to Re: Hash value test of zero by Marshall
in thread Hash value test of zero by themcp

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