It's a case of which error came first.

In this first case, $x[ 0 ] exists, so $x[ -1 ] can be translated as

$x[ @x - 1 ] ==> $x[ 1 - 1 ] ==> $x[ 0 ]

which is valid and currently undef, so the error occurs when try to indirect through undef for the method call. 

P:\test>perl -e" @x = undef; $x[ -1 ]->fred()"
Can't call method "fred" on an undefined value at -e line 1.

[download]

But in this case you have $x[ 0 - 1 ], which translates to a post-normalisetion, negative index (-1), which is illegal.

So that's the error you see, and the indirection is never attempted. 

P:\test>perl -e" $x[ -1 ]->fred()"
Modification of non-creatable array value attempted, subscript -1 at -
+e line 1.

[download]

Of course, the subscript normalisation also incorporates $[, but the always 0...right :)

In reply to Re^5: Negative array subscript method call bug? by BrowserUk
in thread Negative array subscript method call bug? by BUU

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