comment on

I'm not doing something if it is defined, I'm doing it if it's NOT defined.
An annoyance to me (I come from a C background) is a variable failing to be defined does NOT return 0 or a 'FALSE' definition, it returns "". For safety reasons and explicitness, I program in the explicit results of tests i.e. defined $var eq "" or defined var ne "". Using simply 'defined $var' and '! defined $var' isn't as clear as what Perl is doing internally.

If I do print "$3" from a match on 'var = 10' I do not get the same as print "". Regex DO NOT return "" on failing to match, they return undef. After further testing, it appears the difference is where the quantifier comes in:


use strict;
use warnings;

my $string = "string";

if( $string m/([5]?)string/ ){
    print "? inside group: $1\n"; #prints fine
}

if( $string m/([5])?string/ ){
    print "? outside group: $1\n"; #Use of uninitialized value $1 in c
+oncatenation (.) or string...
}

return 0;
[download]

P.s. the reason I'm doing this manually is because I'm making it as portable as possible and sensible to me. I'm running Perl on Windows 7/8/10, modern Linux, a Debian 2.6.32, etc. Production environment with too many distributions, internal/external network, all that jazz. I already had an issue where a CPAN module I would've liked had some Linux-only make commands.

In reply to Re^2: Regex result being defined when it shouldn't be(?) by chenhonkhonk
in thread Regex result being defined when it shouldn't be(?) by chenhonkhonk

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