Given the above, here's a step by step breakdown of what Perl does. 

c: When the code is compiled.
r: When the code is run.

     my @list = x() | (1,2,3);
c => my @list = scalar(x()) | scalar(1,2,3);
c => my @list = scalar(x()) | scalar(2,3);  <<void warn>>
c => my @list = scalar(x()) | scalar(3);  <<void warn (supressed)>>
c => my @list = scalar(x()) | 3;
r => my @list = undef | 3;
r => my @list = 0 | 3; <<uninit warning>>
r => my @list = 3;

     my @list0 = x() || (1,2,3);
c => my @list0 = scalar(x()) || (1,2,3);
r => my @list0 = undef || (1,2,3);
r => my @list0 = (1,2,3);

     my @list1 = x() or (1,2,3);
c => ( my @list1 = x() ) or (1,2,3);
c => ( my @list1 = x() ) or (2,3);  <<void warn>>
c => ( my @list1 = x() ) or 3;  <<void warn (supressed)>>
c => my @list1 = x();  <<void warn>>
r => my @list1 = ();

     my @list2 = $c->bbox('all') || (1,2,3);
c => my @list2 = scalar($c->bbox('all')) || (1,2,3);
r => my @list2 = [ ... ] || (1,2,3);
r => my @list2 = [ ... ];

     my @list3 = $c->bbox('all') or (1,2,3);
c => ( my @list3 = $c->bbox('all') ) or (1,2,3);
c => ( my @list3 = $c->bbox('all') ) or (2,3);  <<void warn>>
c => ( my @list3 = $c->bbox('all') ) or 3;  <<void warn (supressed)>>
c => my @list3 = $c->bbox('all');  <<void warn>>
r => my @list3 = ( ... );

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In reply to Re^2: 'or' versus '||' - Unexpected Results by ikegami
in thread 'or' versus '||' - Unexpected Results by cmv

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