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Re^3: Why does foo() evaluate in array context in "${\foo()}"?

by gone2015 (Deacon)
on Apr 23, 2009 at 10:02 UTC ( [id://759500]=note: print w/replies, xml ) Need Help??


in reply to Re^2: Why does foo() evaluate in array context in "${\foo()}"?
in thread Why does foo() evaluate in array context in "${\foo()}"?

As JavaFan says, contrary to most expectations \ actually provides LIST context ! So:

#!/usr/bin/perl -w use strict ; use warnings ; sub foo { my ($tag) = @_ ; print "$tag: ", wantarray ? "LIST" : "SCALAR", "\n" ; return wantarray ? ('a', 'b') : \78 ; } ; my $a = \foo('SCALAR \foo()') ; my @a = \foo('LIST \foo()') ; my $b = ${foo('SCALAR ${foo()}')} ; my @b = (${foo('LIST ${foo()}')}) ;
gives:
SCALAR \foo(): LIST
LIST   \foo(): LIST
SCALAR ${foo()}: SCALAR
LIST   ${foo()}: SCALAR
which also shows that ${...} does provide SCALAR context as expected.

This behaviour is not mentioned in perlop and I cannot see it in perlref either :-(

It is documented that \($a, @b, %c) is the same as (\$a, \@b, \%c). Which requires the , to be operating in LIST context -- so perhaps we should not be surprised. (It's also worth remembering that LISTs are interpolated when they are evaluated, not when they are constructed...)

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