Confusing Uninitialized warning

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

Having been totally led astray by the enigmatic "Use of uninitialized value in string eq" warning, I am now boggled.

This snippet of code gives the warning "Use of uninitialized value in string eq"

my %data = @_;
warn $data{'FLOATER'};
print $data{'FLOATER'}."<-----------";
if( $data{'FLOATER'} eq 'Y' ){
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This is in a subroutine, hence the use of @_. The warn and print statements are for debugging this warning, and both show this hash key to hold the value "N". A defined($data{'FLOATER'}) returns true. What am I missing?

I have searched for similar problems with this error string, but it is so common that I haven't found anything useful. I have tried different combos of quotes around the hash key, and the constant 'Y'. Nothing seems to matter. I have also seen the same warning with similar code, but different values.

Comment on Confusing Uninitialized warning Download Code

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Re: Confusing Uninitialized warning by kaif (Friar) on Jun 13, 2005 at 16:24 UTC
Do you have an `elsif` or such construct below your posted code? Sometimes Perl reports "strange" locations for errors involving these constructs. See No Pause on Elsif in Debugger for more information.	[reply] [d/l]
Re^2: Confusing Uninitialized warning by spencerogden (Initiate) on Jun 13, 2005 at 17:17 UTC
kaif, You've hit the nail on the head. I guess if an error occurs in elsif statements it reports the line number of the parent if statement. Not very helpful. Thanks, Spencer	[reply]
Re: Confusing Uninitialized warning by ikegami (Patriarch) on Jun 13, 2005 at 16:18 UTC
Maybe the line number in the error message is wrong. That happens (particularly when the error is in an `elsif`). If `defined($data{'FLOATER'})` is true as you say, it makes no sense for the `if` to give you that warning. Update: Additionally, you're probably better off passing the hash by reference. It saves memory, executes faster and preserves `tie` magic. For example: `sub test { my ($data) = @_; ... print($data->{'FLOATER'}); # Need to add "->" ... } my %data = ...; test(\%data);` [download]	[reply] [d/l] [select]
Re: Confusing Uninitialized warning by Joost (Canon) on Jun 13, 2005 at 16:20 UTC
That snippet is perfectly fine. Your problem is somewhere else. Please post code that reproduces the problem. Something other than the following: `#!/usr/bin/perl -w use strict; test( FLOATER => 'N'); sub test { my %data = @_; warn $data{'FLOATER'}; print $data{'FLOATER'}."<-----------"; if( $data{'FLOATER'} eq 'Y' ){ print "Test: yes\n"; } } __OUTPUT__ N at test.pl line 8. N<-----------` [download] "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re: Confusing Uninitialized warning by davidrw (Prior) on Jun 13, 2005 at 16:21 UTC
is that the _only_ warning given? What does `print join ':', @_;` show (so we can see what's in there)? Or may the context in which the sub is being called? This code works fine for me w/no warnings: `use strict; use warnings; my %data = ( FLOATER => 'N', BLAH=>2); warn $data{'FLOATER'}; print $data{'FLOATER'}."<-----------\n"; warn 'ok' if $data{'FLOATER'} eq 'Y';` [download]	[reply] [d/l] [select]