And the use strict; use warnings; advice would have given you an indication:

$ perl -wE'my $item1="x\t\ty";my@tmp1=split(/t+\,$item1/);'
Use of uninitialized value $_ in split at -e line 1.
$ perl -wE'my $item1="x\t\ty";my@tmp=split(/t+/,$item1);say for@tmp'
x               y
$ perl -wE'my $item1="x\t\ty";my@tmp=split(/\t+/,$item1);say for@tmp'
x
y
[download]