use strict;
use warnings;

sub tst {
	warn "entering tst()\n";
	my $arg = shift;  # line 6
	warn "leaving tst()\n\n";
}

my %h=();
tst $h{''};
tst $h{undef};  # line 12
my $bla='';
tst $h{$bla};  # line 14
$bla=undef;
tst $h{$bla};  # line 16
undef $bla;
tst $h{$bla};  # line 19

##</code><code>##

entering tst()
leaving tst()

entering tst()
leaving tst()

entering tst()
leaving tst()

Use of uninitialized value $bla in hash element at perlmonks-1063097.pl line 16.
entering tst()
Use of uninitialized value in scalar assignment at perlmonks-1063097.pl line 6.
leaving tst()

Use of uninitialized value $bla in hash element at perlmonks-1063097.pl line 18.
entering tst()
Use of uninitialized value in scalar assignment at perlmonks-1063097.pl line 6.
leaving tst()