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Re: Looking for pointers or optimizations.

by 2teez (Priest)
on Aug 21, 2012 at 13:47 UTC ( #988733=note: print w/replies, xml ) Need Help??

in reply to Looking for pointers or optimizations.


  • You might want to use "use warnings" instead of "-w", so that you can remove warning using "no warnings" pargma, where you wouldn't want some.
  • Always check the return for the open function like so: open $fh,'<',$filename or die "can't open file: $!" OR you use use autodie qw(open close);
  • The File handler $fh decleared was not used
  • filehandle $fh was not close. You should do that like so:close $fh or die "can't close file:$!"
You really might what to try out the module "perlcritic", based on Damian Conway's book Perl Best Practices. Check Perlcritic
Using it from Command Line Interface like so:
perlcritic -3

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Re^2: Looking for pointers or optimizations.
by greengaroo (Hermit) on Aug 21, 2012 at 14:24 UTC

    Please correct me if I am wrong (sometimes I am) but I think that no warnings; works for the -w switch too. I was asking myself the same question a while ago. Try this:

    #!/usr/bin/perl5.10 -w my %hash1 = { test1 => 'test1', test2 => 'test2' }; no warnings; my %hash2 = { test1 => 'test1', test2 => 'test2' }; use warnings; my %hash3 = { test1 => 'test1', test2 => 'test2' };

    I get:

    Reference found where even-sized list expected at ./ l +ine 3. Reference found where even-sized list expected at ./ l +ine 15.

    Now the question is, what is the difference if any between the -w switch and use warnings;?

    Update: Answering myself, on perldoc it says: The warnings pragma is a replacement for the command line flag -w , but the pragma is limited to the enclosing block, while the flag is global.

    Take my advice. I don't use it anyway.

      I very recently encountered a spurious(?) error message (on v5.8.2):

      Use of uninitialized value in substitution (s///) at (eval 2) line 21

      Which resulted from the addition of one line like this:

      $hash{$var1}{'string'} = $var2;

      I confirmed that the variables were defined, and that the hash entry was created. I then tried:

      { no warnings 'uninitialized'; # and later: no warnings; $hash{$var1}{'string'} = $var2; }

      To no avail. Curiously, the error wasn't occurring at that line (confirmed with print statements); but it disappeared if I commented out that line.

      Removing -w got rid of the error.

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