$a x= 2**31; creates an empty string,

Look again: 

C:\test>perl
$a = chr(0); $a x= 2**31;
print length $a;
substr( $a, 0, 2**16 ) =~ tr[\0][\1];
substr( $a, 2**16, 2**16 ) =~ tr[\0][\1];
^Z
substr outside of string at - line 3.
2147483648

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In reply to Re^2: substr outside of string? by BrowserUk
in thread substr outside of string? (Updated: Fixed in later builds.) by BrowserUk

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