Maybe you should not ignore strict and the other things. You might have got some indication on your mistakes (although I can't check that now, having no environment right now).

[1,2,3] is not an array but a reference to an array. So you may want

my $a = [1, 2, 3];
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or

my @a = (1, 2, 3);
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This also does not work:

foreach $a[1](@b)
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Maybe you want something this:

foreach @$a[1][@b]
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but I am really not sure, because the inner array has not been initialized. Finally,

$a[1]
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is also probably wrong, since @a is a reference to an array. Please explain what you are really trying to do, I can't really figure out.