my %h = ("\0011\002\r\n\t\f\"\\abcdefghijklmnopqrstuvwxyz", undef);
$v = join '', %h;
EXPECT
-Use of uninitialized value $h{"\0011\2\r\n\t\f\"\\abcdefghijkl"...} in join or string at - line 6.
+Use of uninitialized value $h{"\0011\2\r\n\t\f\"\\abcdefghijklm"...} in join or string at - line 6.
########
use warnings 'uninitialized';
my ($m1, $v);
$v = eval $m1;
EXPECT
Use of uninitialized value $_ in eval "string" at - line 4.
-Use of uninitialized value $_ in eval "string" at - line 4.
-Use of uninitialized value $_ in eval "string" at - line 4.
-Use of uninitialized value $m1 in eval "string" at - line 5.
-Use of uninitialized value $m1 in eval "string" at - line 5.
Use of uninitialized value $m1 in eval "string" at - line 5.
########
use warnings 'uninitialized';