...

my @Outcond = ([]);                    #array for out conditions

...

sub Outcond {
    my( $twig, $s )= @_;
    push(@{$Outcond[$#Outcond]},( $s->att('NAME')));
}

...

sub Output {
    my( $twig, $s )= @_;
    push(@Jobs,( $s->att('JOBNAME')));
    push(@Time,($s->att('TIMEFROM')));
    push(@Desc,($s->att('DESCRIPTION')));
    push(@Days,($s->att('DAYS')));
    push(@Outcond, []); #At the end you will have a trailing empty arrayref at the end of @Outcond, but you don't need to worry about that given the way you print your output
}

...

sub write_text {
    my $worksheet = shift;                                            

    ...

    #loop all data and output in correct positions
    while ($count <= (scalar(@Jobs))) {
        $worksheet->write($ygroup, $xgroup, $group[$count-1]);
        $worksheet->write($yjobs++, $xjobs, $Jobs[$count-1]);
        $worksheet->write($yDays++, $xDays, $Days[$count-1]);
        $worksheet->write($yTags++, $xTags, $Tag[$count-1]);
        $worksheet->write($yStarting++, $xStarting, $Time[$count-1]);
        $worksheet->write($yDesc++, $xDesc, $Desc[$count-1]);
        $worksheet->write($yOut++, $xOut, join(',', @{$Outcond[$count-1]});
        $worksheet->write($yIn++, $xIn, $Incond[$count-1]);    

        $ygroup = ($ygroup+$yjobs);    
        $count++;
    }
}