1nickt is right: few notes more

push already accept a list: push @{$myarr[$index][$subindex]}, [ @tmp ] has to be push @{$myarr[$index][$subindex]}, @tmp infact i suspect 23 is number of elements in @tmp

Also scalar(@{$myarr[$index]})-1) can be written as $#{$myarr[$index]}

L*