Re: Annoying 'Use of uninitialized value in concatenation' warning

If you want to make the undef value obvious in the output then you could:

use warnings;
use strict;
use 5.010;

my @some_array = (1, 2, undef, 4, 5);

for (my $ii = 0; $ii < scalar(@some_array); $ii++) {
    print "Value at position $ii: @{[$some_array[$ii] // '--undef--']}
+\n";
}
[download]

Prints:

Value at position 0: 1
Value at position 1: 2
Value at position 2: --undef--
Value at position 3: 4
Value at position 4: 5
[download]

True laziness is hard work

Comment on Re: Annoying 'Use of uninitialized value in concatenation' warning Select or Download Code

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Re^2: Annoying 'Use of uninitialized value in concatenation' warning by NoobForever (Initiate) on Feb 04, 2015 at 17:36 UTC
another option without concatenation: `print "Value at position $ii: ", $some_array[$ii] \|\| '--undef--',"\n";` [download]	[reply] [d/l]
Re^3: Annoying 'Use of uninitialized value in concatenation' warning by AnomalousMonk (Archbishop) on Feb 04, 2015 at 18:00 UTC
The problem with using the `\|\|` (logical-or) operator (see perlop) in this case is that the undefined value is false, as are 0, '0' and '' (the empty string), and `\|\|` does not distinguish. If your Perl version is 5.10+, you can use the `//` (defined-or) operator; otherwise, you're stuck with syntax that's a bit more messy: `c:\@Work\Perl\monks>perl -wMstrict -le "use 5.010; ;; my @ra = (0, 0, 0); ;; my $i = 1; print qq{value at index $i: }, $ra[$i] \|\| 'undef'; print qq{value at index $i: }, $ra[$i] // 'undef'; print qq{value at index $i: }, defined($ra[$i]) ? $ra[$i] : 'undef' " value at index 1: undef value at index 1: 0 value at index 1: 0` [download] Give a man a fish: `<%-(-(-(-<`	[reply] [d/l] [select]