The best workaround I've found is to modify the string in-place by using the 4-arg substr. This effectively just adjusts a pointer and a couple of offsets, and so runs 1000x faster: 

c:\test>TimeIt \perl\bin\perl.exe 
    -e"$a = 'a' x 800_000; substr($a, 0, 1, '') while length($a);"
 Kernel: 0.00000 User: 0.26563 Total: 0.26563

[download]

Unfortunately, it isn't a good substitute for the lvalue ref problem.

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In reply to Re: Using substr to split a string scales as N^2 -- alternatives? by BrowserUk
in thread Using substr to split a string scales as N^2 -- alternatives? by hrr

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