comment on

perl -le 'my $f = 1; ($f > 0 ? @a : $a ) = ("a", "b", "c")'
Assignment to both a list and a scalar at -e line 1, at EOF

Keep in mind that there are two different "=" operators: the list assignment operator (aassign) and the scalar assignment operator (sassign). The selection of the operator is based on whether the LHS of the assignment is list-ish or scalar-ish. The reason the above doesn't compile isn't the inability to change context at run-time, it's the inability to select an operator.

The two operators compared:

	Context Imposed on Operands	Stack on Input	In	Evaluates To	Stack on Output
`sassign`	scalar	Two SVs	scalar	LHS as an alias	One SV
`sassign`	scalar	Two SVs	list	LHS as an alias	One SV
`lassign`	list	Two marked lists of SVs	scalar	Number of items in list returned by the RHS	One SV
`lassign`	list	Two marked lists of SVs	list	LHS as a list of aliases	One (unmarked) list of SVs

Notice the significant differences in how Perl needs to setup the stack before the operator is called, making the choice of operators crucial.

In reply to Re: Context: compile-time vs. run-time by ikegami
in thread Context: compile-time vs. run-time by shmem

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