unititialized value warning

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

Hi fellow monks,

What is my code doing that warrants a warning, and how do I fix it? Thanks. Abridged warnings:

Use of uninitialized value in length at ./jumble.pl line 34, <DATA> li
+ne 1.
Use of uninitialized value in split at ./jumble.pl line 34, <DATA> lin
+e 1.
Use of uninitialized value in concatenation (.) or string at ./jumble.
+pl line 36, <DATA> line 1.
Use of uninitialized value in split at ./jumble.pl line 33, <DATA> lin
+e 1.
[download]

The offending code

use strict;
use warnings;
use List::Util 'shuffle';

while (<DATA>) {
    my @newline = split(/\b/);
    for my $word (@newline) {
        my $first = "";
        my $rem = "";
        my $middle = "";
        my $last = "";
        ($first, $rem)  = split /(?<=\b\w)/, $word;
        ($middle, $last) = split /(?=(\w'\w+|\w)$)/, $rem;
        ((length $middle) == 2) ? $middle = reverse $middle :
        ($middle = join "", shuffle(split //, $middle));
         print "$first$middle$last";
    }
}
[download]

__END__
I couldn't believe that I was actually understanding what I was readin
+g.
The phenomenal power of the human mind, according to research at Cambr
+idge University,
suggests that it doesn't matter in what order the letters in a word ar
+e, as long as
the first and last letters are in the right place. The rest can be a t
+otal mess,
and you can still read it without a problem. This is because the human
+ mind does
not read every letter by itself, but the word as a whole. Amazing, huh
+? Yeah,
and I always thought spelling was important!
Check apostrope and punctuation: Jame's, They're, we'll they'd.
[download]

And here's the output, with warnings off: I cdolun't beievle taht I was aalulcty uedsnadnnitrg waht I was rdaenig. The peeaonhmnl peowr of the hmuan mnid, adcircnog to rerecash at Cibmdarge Uteirsvniy, ssugetgs taht it dosen't mettar in waht odrer the lterets in a wrod are, as lnog as the fisrt and lsat ltteres are in the rghit pcale. The rset can be a toatl mses, and you can siltl raed it woihtut a pboerlm. Tihs is bceusae the hmuan mnid deos not raed eervy lteetr by iseltf, but the wrod as a wlhoe. Ainzamg, huh? Yaeh, and I ayawls tguhhot splileng was intpaormt! Cchek asoptorpe and puttiunoacn: Jmae's, Tehy're, we'll tehy'd.

Comment on unititialized value warning Select or Download Code

Replies are listed 'Best First'.
Re: unititialized value warning by ikegami (Patriarch) on Mar 14, 2010 at 01:45 UTC
"Note that splitting an EXPR that evaluates to the empty string always returns the empty list, regardless of the LIMIT specified." `$rem` holds an empty string, so an empty list is assigned to `($middle, $last)`, setting `$middle` and `$last` to undef. Fix: use strict; use warnings; use List::Util qw( shuffle ); while (<DATA>) { s/(?<=\w)(\w+)(?=\w)/ join('', shuffle($1=~m{.}sg)) /eg; print; } __DATA__ I couldn't believe that I was actually understanding what I was reading. The phenomenal power of the human mind, according to research at Cambridge University, suggests that it doesn't matter in what order the letters in a word are, as long as the first and last letters are in the right place. The rest can be a total mess, and you can still read it without a problem. This is because the human mind does not read every letter by itself, but the word as a whole. Amazing, huh? Yeah, and I always thought spelling was important! Check apostrophe and punctuation: Jame's, They're, we'll they'd. [download] By the way, try replacing `shuffle($1=~m{.}sg)` [download] with `sort $1=~m{.}sg` [download] It'll probably be harder to read.	[reply] [d/l] [select]
Re^2: unititialized value warning by wrinkles (Pilgrim) on Mar 14, 2010 at 02:33 UTC
Thanks ikegami, I just needed to check the variables. This fixed it: `use strict; use warnings; use List::Util 'shuffle'; while (<DATA>) { my @newline = split(/\b/); for my $word (@newline) { my $first = ""; my $rem = ""; my $middle = ""; my $last = ""; ($first, $rem) = split /(?<=\b\w)/, $word if $word; ($middle, $last) = split /(?=(\w'\w+\|\w)$)/, $rem if $rem; ((length $middle) == 2) ? $middle = reverse $middle : ($middle = join "", shuffle(split //, $middle)) if $middle; print "$first" if $first; print "$middle" if $middle; print "$last" if $last; } }` [download]	[reply] [d/l]