avoid uninitialized values for $

GertMT has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,
I'm dealing with some csv-files that I use as a basis to make various calculations. It all works fine and the calculations are correct except that while using:

#!/usr/bin/perl -w # use warnings
use strict;
use diagnostics;
[download]

I remain having the problem that I frequently get the message:
Use of uninitialized value in numeric eq (==) at
The reason for these warnings are probably 'missing values' in the csv-file. $_ will be undefined as I understood from documentation. While using things like (as mentioned in an earlier post):

use Data::Table;
$joinTable->colsMap( sub { $_->[4]  = skipblanks( $_->[4] ) } );

sub skipblanks {
    my @data = @_;
    my $x    = 0;
    foreach $x (@data) {
        if ($x) {
            $x =~ s/,/\./g;
        }
        return $x;
    }
}
[download]

use Data::Table;
$joinTable->colsMap( sub { $_->[4]  = to_int_or_zero( $_->[4] ) } );

sub to_int_or_zero {
    my $value = shift;
    if (
        defined($value)
        && (   $value =~ m/^\d+$/
            || $value =~ m/^-?\d+\.?d*$/ )
      )
    {
        return $value;
    }
    else {
        return 0;
    }
}
[download]

The message is still appearing sometimes. What am I doing wrong? Maybe not ideal in every situation but what would work for me is to fill all blanks with '0' (zeroes). Is there a way to do this for the whole csv-file at the beginning of the script. Or maybe some other straightforward or generic way to make $_ always initialized in order to avoid the warnings?
Thanks,
Gert

Comment on avoid uninitialized values for $_ Select or Download Code

Replies are listed 'Best First'.
Re: avoid uninitialized values for $_ by lima1 (Curate) on Nov 06, 2007 at 12:34 UTC
If you just want to avoid the warnings, you can always inhibit them with no warnings. See perllexwarn. `use warnings; .. # in the block no warnings qw(uninitialized);` [download] Are you aware that skipblanks() does not iterate over @data? The following code should do the same as your function: `sub skipblanks { # my @data = @_; # you probably want $x = shift \|\| 0; my $x = shift; # foreach $x (@data) { if ($x) { $x =~ s/,/\./g; } return $x; # } }` [download]	[reply] [d/l] [select]
Re^2: avoid uninitialized values for $_ by GertMT (Hermit) on Nov 06, 2007 at 12:51 UTC
thanks for your reply, Very good for pointing me to that guess I shoud have used 'next' or something like that. With your proposed improved skipblanks() it seems to work better! I keep the other suggestion 'no warnings' as a reserve. Thanks, Gert	[reply]


"be consistent"
	PerlMonks

avoid uninitialized values for $_