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in reply to Transitive aliases

This may be missing the mark, because I don't understand your goal; but for the way switch_var is supposed to work, inside of that sub you could tie $w. Then setting it elsewhere in the program automatically sets $r. Based on my rememberance of subroutine prototypes, maybe something like: 

sub switch_var (\$$\$) {
    my ($reference, $initial, $binding) = @_;
    # bind $binding to scalar reference $reference
    tie $$binding, 'SomeClass', $reference;
    $$binding = $initial;
}

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where SomeClass is a simple scalar tied package that implements at least TIE to store $reference and STORE to set @$reference = ($value) x $something.

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Re^2: Transitive aliases
by JadeNB (Chaplain) on Dec 28, 2009 at 03:18 UTC

    This is a good idea, although I think I may have made the problem statement over-specific—I'd really like to be able to handle any circular reference, not just a reference to an array of several copies of a single variable. Thus, maybe the appropriate thing to do would be 

    sub switch_var {
    tie $_[2], to => $_[1];
}

package to;
sub TIESCALAR {
    bless \$_[1] => $_[0];
}

sub STORE { ${$_[0]} = $_[1] }

sub FETCH { ${$_[0]} }

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    (There's some package out there already on CPAN that uses the to package for similar effect, but I can't find it. UPDATE: It's Tie::Util. Also, the functionality that I've described is quite similar—indeed, maybe identical—to that provided by Tie::Coupler.)

    I wonder if there's a non-tie-based solution? I might have to do switch_var several times, and going through many ties could get quite slow.

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