Add array to hash in perl - arrays

Question

I try to add array in hash.
if ( not exists $hashtime{ $arr[0] }{ $date }{ $hour }{ $min } ) {
print "$min not exist";
$hashtime{ $arr[0] }{ $date }{ $hour }{ $min } = [ $sec ];
$create++;
};
And received the error:
Not a HASH reference at ./sort_log_by_ip.pl line 63, line 1.
Why is this code wrong?
In perldoc perldsc I see this construction, and I'm using something similar:
while ( <> ) {
next unless s/^(.*?):\s*//;
$HoA{$1} = [ split ];
}
Update
Code before:
if ( not exists $hashtime{ $arr[0] } ) {
$hashtime{ $arr[0] } = ( $date => { $hour => { $min => [ $sec ] } } );
$create++;
print "create for IP: $arr[0]\n";
}
if ( not exists $hashtime{ $arr[0] }{$date} ) {
$hashtime{ $arr[0] }{ $date } = ( $hour => { $min => [ $sec ] } );
$create++;
print "create for IP: $arr[0] DATE: $date\n";
}
if ( not exists $hashtime{ $arr[0] }{$date}{$hour} ) {
$hashtime{ $arr[0] }{ $date }{ $hour } = ( $min => [$sec] );
$create++;
print "create for IP: $arr[0] DATE: $date HOUR: $hour\n";
}

Answer 1

You are using a list ( ) instead of a hash reference { }, in all if blocks.
When you say
$hashtime{$arr[0]} = ( $date => { $hour => { $min => [$sec] } } );
because of LIST ( ) being evaluated in scalar context what happens is equivalent to
$hashtime{$arr[0]} = ( $date, { $hour => { $min => [$sec] } } );
ending up as
$hashtime{$arr[0]} = { $hour => { $min => [$sec] } };
since the , operator evaluates and discards operands one at a time, returning the last one.
The next if goes similarly and you then have either of (or both)
$hashtime{$arr[0]}{$date}{$min}{[$sec]}
$hashtime{$arr[0]}{$hour}{$min}{[$sec]}
However, the code that draws the error
if (not exists $hashtime{$arr[0]}{$date}{$hour})
needs a hashref at both $arr[0] and {$date}, while it clearly doesn't have both.
In both if blocks you need to assign a hash reference, obtained using { }
$hashtime{$arr[0]} = { $date => { $hour => { $min => [$sec] } } };
and
$hashtime{$arr[0]}{$date} = { $hour => { $min => [$sec] } };
as well as in the last if block.
Please indent your code properly. It is very hard to work with it the way it was posted.