G'day rmarkman,

Welcome to the Monastery.

Update (strike): I looked up the error message and made an incorrect inference. I suspect I read "off the end of the string" as "off the end of the array". Anyway, regardless of the reason, what I wrote is wrong and is now stricken.

Your split statement, as written, only produces 6 elements: ('A' .. 'F'). You can print $#flds or scalar(@flds) to confirm this.

When you add a LIMIT of -1, you get 10 elements. This behaviour is documented in split: there's examples roughly in the middle of the page.

With the code as posted, both $flds[16] and $flds[8] are undefined. Attempting to assign undef doesn't cause an issue:

$ perl -we 'undef=undef'
$
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Attempting to assign 0 generates the error you're getting:

$ perl -we 'undef=0'
Modification of a read-only value attempted at -e line 1.
$
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If you use split like this:

@flds = split(/(\t)/, $value);
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You'll get 18 elements. That's also documented (at the end of the page).