Proof of concept

#!/usr/bin/perl --
BEGIN{
package PPI::Transform::ConditionalAssignment;
use strict;
use warnings;
use Params::Util   qw{_STRING _INSTANCE};
use PPI::Transform ();
use parent 'PPI::Transform';
our $VERSION = '0.1'; # VERSION
sub document {
    my $self     = shift;
    my $document = _INSTANCE(shift, 'PPI::Document') or return undef;
    my $elements = $document->find( sub {
        $_[1]->isa('PPI::Token::Operator') or return '';
        $_[1]->content eq '?'     or return '';
        $_[1]->snext_sibling->isa('PPI::Token::Operator') or return ''
+;
        $_[1]->snext_sibling->content eq '='     or return '';
        return 1;
    } );
    return undef unless defined $elements;
    return 0 unless $elements;
    my $changes = 0;
    foreach my $question ( @$elements ) {
        my $symbol = $question->sprevious_sibling->clone;
        my $equals = $question->snext_sibling;
        $equals->insert_after( $symbol );
        $symbol->insert_after( $question->remove );
        $changes++;
    }
    return $changes;
}

1;
$INC{'PPI/Transform/ConditionalAssignment.pm'}=__FILE__;
} # BEGIN
package main;
use Filter::PPI::Transform 'PPI::Transform::ConditionalAssignment';
for my $foo ( 0 .. 1 ) {
    my $bar = $foo;
    $foo ?= 'one' : 'zero';
    print "$foo\n";
    $bar ?= ('one '.rand): ('zero '.rand);
    print "$bar\n";
}
print "let me know " ? "should I stay" : "or should I go";
__END__
$ perl ppi-transform-conditional-assignment.pl
zero
zero 0.563323974609375
one
one 0.086761474609375
should I stay
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