Try running the code with 
sub qqq {
    return "triple q"
}

[download]

The /ee does kind of a double evaluation. First, "$rhs" is evaled, returning qqq, and this is run as a Perl expression. If qqq is not declared, the eval returns undef that you see reported in the warning.

'$rhs', on the other hand, is evaled to $rhs which being run as a Perl expression returns qqq.

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re: /ee -> Use of uninitialized value in substitution iterator (without back references) by choroba
in thread /ee -> Use of uninitialized value in substitution iterator (without back references) by karlberry

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