I've bumped into a rather odd problem when trying to use some of the aggregate DBI functions, like selectcol_arrayref. Since many of them return array references, I tend to dereference the array when I call the method. For example, 
@ary = @{$dbh->selectcol_arrayref($sql)};

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My problem occurs when the statement in $sql returns zero rows. Consider the following script: 
#!/usr/bin/perl -w
use strict;
use DBI;
$\ = "\n";
# Input dbname, user & pass on the command line
my ($dbname, $dbuser, $dbpass) = @ARGV;

my $dbh = DBI->connect("DBI:Oracle:$dbname", $dbuser, $dbpass, {RaiseE
+rror => 1}) or die $DBI::errstr;

# This query returns no rows
my $sql = qq~ SELECT dummy FROM dual WHERE dummy = '1' ~;

# This works just fine...
my $ref = $dbh->selectcol_arrayref($sql) or die $dbh->errstr, $!;
print "\$ref is defined: $ref" if defined $ref;
print for @$ref;

# But this one dies!
my @ary = @{$dbh->selectcol_arrayref($sql)} or die $dbh->errstr, $!;
print for @ary;

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In the second attempt to make the query, $dbh->errstr is undef, meaning that the DB query worked fine. But, </code>$!</code> contains this: 
No such file or directory at ./dbtest.pl line 17.

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If I remove the die, everything works the way I want it to, but I would like to know why it is dying to begin with.

In reply to Dereferencing and DBI methods by Cirollo

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