Okay, you made $R lexical with my. ${R} is a symbolic reference to the scalar variable named 'R'. Just left alone, Perl will figure out you want the lexical variable and not a variable in the symbol table.

Looking for ${R}[0], however, perl -w says this:
Name "main::R" used only once: possible typo at - line 2.

So, when you add characters that look like a variable specification Perl is only looking in the symbol table.

If you don't make $R lexical, it will work like you originally expected:

$R="foo";
print "${R}[0]\n";
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prints "foo[0]"

To get perl to keep interpolating, just keep adding {}'s:

use vars qw/$R @foo/;
$R="foo";
@foo = (42);
print "${${R}}[0]\n";
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prints 42

:-)

BTW, I seem remember some code posted some time ago which did this kind of "multiple interpolation." I can't find it. Anyone know what node that is (or am I just hallucinating again?
("Too much LDS" -- Kirk about Spock in ST:IV))

Update: Here it is: Double Interpolation of a String

Russ
Brainbench 'Most Valuable Professional' for Perl