[Perl-beginners] Use of uninitialized value

if you are using :
use warnings;

Then you can use 'no warnings;' just like you would use 'use warnings' to turn off. Then you can use 'use warnings' to get it goint again. The better point might be to surround what you want within {}'s and use your 'no warnings' and once you hit the ending }, then will return to using warnings again.

Wags ;)


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You can be a little more specific with:

no warnings qw( uninitialized ); # see `perldoc perllexwarn`

You could also use a default value;

my $value = fetch_value() || '';

or what most seem to do is combine the tests:

if ( defined( $value ) && $value eq 'some_value' ) { ... }

It is a terrible thing, not because it's slower: On a modern machine
(especially now that speculative execution is a pretty much Solved
Problem) a single branch not taken adds at WORST a nanosecond to
your program. Even on a vintage 1988 Sun3 a single branch-not-taken
is going to add maybe 50 nanoseconds.

If there were one thing I could beat into the brains of all the
beginners on this list:

Do not write code that you think will be
fast. Write code that you think will work.

The reason it is a terrible thing is because you must have two
copies of "other stuff", and the odds of those two copies remaining
identical grows slimmer each day.
The idiom I use every single day:

#!/usr/bin/perl

use strict;
use warnings;
use diagnostics;


my $value;

if ($value && $value eq 'spring' ) {
print "Flowers are in bloom\n";
} else {
print "No flowers here!\n";
}

-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Lawrence Statton - [email protected] s/aba/c/g
Computer software consists of only two components: ones and
zeros, in roughly equal proportions. All that is required is to
sort them into the correct order.

[email protected] wrote:

: The idiom I use every single day:
:
: #!/usr/bin/perl
:
: use strict;
: use warnings;
: use diagnostics;

My idiom, which is used a lot for testing code on
various beginner lists, is this. I never did care for the
verbose output of diagnostics.pm.

#!/usr/bin/perl

use strict;
use warnings;

#use Data::Dumper 'Dumper';
#use CGI;

__END__


I also have a few editor macros on hand like this one
for file opening.

CTRL+ALT+F:

my $file = '';
open FH, $file or die qq(Cannot open "$file": $!);

close FH;


HTH,

Charles K. Clarkson