You can silence the warning (if you know what you do) or you can detect and treat the undef-case. However, it is wise to keep the no warnings; scope small.
Update: See also johngg's hint below about the do{ ... } trick.
When in doubt, I suggest to treat the undef-case, and let the warning pragma do its job.
Often, an undef warning reveals a bug that was otherwise undetected.
use strict;
use warnings;
sub original_post {
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]\n";
}
}
sub detect_undef_and_set {
my @some_array = (1, 2, undef, 4, 5);
#alternative-1: fix data structure
# @some_array = map { $_ // '(oops! undef!!)' } @some_array;
for (my $ii=0; $ii < scalar(@some_array); $ii++) {
#alternative-2: fix output
print "Value at position $ii: ", $some_array[$ii] // '(oops! undef
+!)' , "\n";
}
}
sub no_warnings {
my @some_array = (1, 2, undef, 4, 5);
for (my $ii=0; $ii < scalar(@some_array); $ii++) {
no warnings 'uninitialized'; # for this lex scope only
print "Value at position $ii: $some_array[$ii]\n";
}
}
print "ORIG:\n"; original_post();
print "CHECK:\n"; detect_undef_and_set();
print "NO WARN:\n"; no_warnings();
__DATA__
RIG:
Value at position 0: 1
Value at position 1: 2
Use of uninitialized value $some_array[2] in concatenation (.) or stri
+ng at nowarn.pl line 7.
Value at position 2:
Value at position 3: 4
Value at position 4: 5
CHECK:
Value at position 0: 1
Value at position 1: 2
Value at position 2: (oops! undef!)
Value at position 3: 4
Value at position 4: 5
NO WARN:
Value at position 0: 1
Value at position 1: 2
Value at position 2:
Value at position 3: 4
Value at position 4: 5
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