my @images = qw/IMAGE1 IMAGE2 IMAGE3 IMAGE4 IMAGE5 
                IMAGE6 IMAGE7 IMAGE8 IMAGE9 IMAGE10
                IMAGE11/;
my @lol;
while ( @images ) {
   push @lol, [ map { (@images) ? shift @images : undef } 1..3 ];
}
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An artifact of this method is that if your initial array has a number of elements not evenly divisible by three you'll get one or two final elements that equate to undef in the last element in @lol.