I guess because undef in an integer context will be taken as '0' (albeit with a warning if you have asked for warnings), whereas -1 is not a valid array index: 

@b = (a .. z);
                                                                      
+          
$#b = undef;
                                                                      
+          
print "@b";
                                                                      
+          
$#b = -1;
                                                                      
+          
print "@b";

[download]

/J\

In reply to Re^3: literal lists by gellyfish
in thread literal lists by danmcb

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