I was recently bitten by a bug in my code, where I accidentally wrote 
 
$_{foo}; #$_ containts a hashref.

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I had meant to use $$_{foo}, but was suprised that despite using strict and warnings, perl had seemingly autodeclared %_.
My original code read something like this, to show it isn't completely contrived. 
use strict;
use warnings;
use DBI;
use Data::Dumper;

#connect and execute stored procedure 
#...
push @results, $_{user_id} 
     while ($_ = $sth->fetchrow_hashref());
print Dumper(\@results);

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Which prints 
$VAR1 = [
          undef,
          undef,
          undef
        ];

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I soon spotted the problem, caused by my ever shoddy typing. However a trip to perlvar failed to enlighten. Further investigation revealed that %_ does indeed exist, but is perhaps unused. 'What is %_' was asked a little over 7 years, but didn't elicit a definitive answer.

What is %_ for? If there is no current use, would anyone care to suggest what %_ might be used for?

In reply to Does %_ have a function or is it just for fun? by larard

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