in reply to avoiding hash key typos

use warnings;
use strict;
my $X;
$X->{aa} = 1;
my $c =  $X->{ab};
print "$c\n";

[download]
I get error: Use of uninitialized value in concatenation (.) at p1.pl line 6.

Replies are listed 'Best First'.
Re^2: avoiding hash key typos
by shemp (Deacon) on Apr 14, 2005 at 23:48 UTC
    Yep, you sure do.

    Im thinking more along the lines of when a hash key is supposed to be used in more than one place in a script and it is misspelled in one or more of them.

[reply]
      Note that that error is not directly because the hash key is invalid. This would produce the same error: 
      my $c = undef;
print "$c\n";

      [download]
      Anon's sample only emits a warning because it's using the bad value for something that doesn't accept undef's... but if you were doing something like the following, you would get silent failure/undesired results: 
      my $ct = $dbh->selectrow_array("SELECT ... WHERE x = ?",{},$c);

      [download]
[reply]
[d/l]
[select]
Re^2: avoiding hash key typos
by Mabooka-Mabooka (Sexton) on Apr 17, 2005 at 21:42 UTC
    "Use of uninitialized value in concatenation (.) at ..." is not an error. Unfortunately...

    I am used to seeing it quite often; God knows what the code around me does:-). Consider: 
    #!/usr/local/bin/perl -w
use warnings;
use strict;

my %report_hash = (
    'event_1_count'  => 17,
    'event_2_count'  => 53,
    'event_3_count'  => 1245,
                );

my $salary = $report_hash{'salary'};
print "Conratulations! Your salary this month: $salary dollars.\n";
print "... and my reporting Camel goes on and on...\n";

# Now, this should do it:
die "Oops... I did it again!.." unless exists($report_hash{"salary"});

    [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom