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in reply to Little annoying mistakes ... of others

szabgab,
I am sure I could come up with a laundry list but my mind is on other things (family isn't feeling well). The one that bugs me is not considering defined values that evaluate to false when setting up a conditional. Since I am guilty of this, let me give an example: 
#!/usr/bin/perl
use strict;
use warnings;

my $file = $ARGV[0] or die "Usage: $0 <input_file>";
open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $
+!";

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While I think it is uncommon that someone would name their file '0', it is possible. In other examples, the oversight might be the empty string ''. As a reference, see True and False (aka Booleans). I know that 5.10 introduced the // operator which is great.

Cheers - L~R

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Re^2: Little annoying mistakes ... of others
by toolic (Bishop) on Dec 07, 2008 at 02:59 UTC
    Along the sames lines, and much more likely, is to pass in a numeric option on the command line whose value is quite probably 0. For example, I have a histogram script in which I can pass in the minimum value. Unless I check the value using defined, the thing just doesn't work right: 
    use strict;
use warnings;

use Getopt::Std;
our $opt_m;
getopts('m:');
print "$opt_m\n" if ($opt_m);           # Wrong
#print "$opt_m\n" if (defined $opt_m);  # Right

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