Strange behaviour of Perl's push function - arrays

Question

I am writing a dedicated ICS (iCalendar file) parser.
I pass an array to a subroutine. All variables are single values apart from $notdates which is a comma-separated list of dates.
#entryl = ($dtstart, $dtend, $attendee, $lastmod, $uid, $notdates);
&entrytoarray(#entryl);
sub entrytoarray {
# print Dumper #_;
my $shiftdur = (&stamptoepoc($_[1]) - &stamptoepoc($_[0])) / 60 / 60;
my $attendee = $_[2];
my $deleted = $_[5];
$attendee =~ /ATTENDEE;USER-KEY=([^;]*);CN=([^;]*);.*:(.*)/;
my %ehash = (
"STARTDATE" , &stamptodate($_[0]),
"ENDDATE" , &stamptodate($_[1]),
"STARTSTAMP" , $_[0],
"ENDSTAMP" , $_[1],
"USERKEY" , $1,
"CN" , $2,
"EMAIL" , $3,
"LASTMOD" , $_[3],
"UID" , $_[4],
"DURATION" , $shiftdur
);
# Only keep current data
my $fdays = 4;
my $tdays = 7;
chomp(my $curstamp = `TZ="UTC" date -d "$fdays days" +"%Y%m%d%H%M00"`);
chomp(my $stpstamp = `TZ="UTC" date -d "$tdays days" +"%Y%m%d%H%M00"`);
if (($_[0] > $curstamp) && ($_[1] < $stpstamp)) {
if (defined($deleted)) {
my #deleted = split /,/, $deleted;
foreach (#deleted) {
if ($_ ne $_[0]) {
push(#entry, \%ehash);
}
}
}
else {
push(#entry, \%ehash);
}
}
print Dumper #entry;
This works mostly as expected:
$VAR1 = {
'DURATION' => '5',
'STARTSTAMP' => '20141122230000',
'UID' => '20141114T010539Z--1092363482',
'LASTMOD' => '20141118214419',
'STARTDATE' => '2014-11-22 23:00:00',
'EMAIL' => 'xxxxxxxxxxxxx',
'ENDDATE' => '2014-11-23 04:00:00',
'CN' => 'xxxxxxxxxxx',
'ENDSTAMP' => '20141123040000',
'KEY' => 'xxxxxxxxxxxxxxxxxx'
};
$VAR2 = {
'EMAIL' => 'xxxxxxxxxxxxx',
'ENDDATE' => '2014-11-23 23:00:00',
'ENDSTAMP' => '20141123230000',
'KEY' => 'xxxxxxxxxxx',
'CN' => 'xxxxxxxxxxxxxx',
'STARTDATE' => '2014-11-23 19:00:00',
'LASTMOD' => '20141118205901',
'UID' => '20141114T010456Z--1092363482',
'DURATION' => '4',
'STARTSTAMP' => '20141123190000'
};
$VAR3 = $VAR2;
Where is the $VAR3 = $VAR2 coming from?

Answer 1

My guess is that this section is the culprit:
foreach (#deleted) {
if ($_ ne $_[0]) {
push(#entry, \%ehash);
}
}
If you have several values in the array, the if-statement can be true twice, and thus push a value twice. Unless this is wanted behaviour, I would make sure that only one value is pushed. You can do this by using grep instead:
if (grep { $_ ne $_[0] } #deleted) {
push #entry, \%ehash;
}
Note that this replaces the foreach loop.

Answer 2

Your array #entry contains hash references. Data::Dumper is saying that the first and second elements of the array refer to two different hashes, while the third refers to the same hash as the second.
You don't show where #entry comes from, but I would expect all three elements to be references to %ehash.
The problem is that, if you keep pushing a reference to %ehash onto #entry, they all point to the same data item, and the intermediate states of the hash won't be recorded.
Unless you mean entrytoarray to push only one copy of %ehash (in which case there's a separate problem that we can't see) you need to fix it by either writing
push #entry, { %ehash }
which copies the hash and returns a reference to the copy, or you can declare and populate %ehash inside the foreach loop, which will create a new hash each time around the loop.