Why it's stupid to `use a variable as a variable name'

Update:

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"use warnings;
 use strict;
 ;;
 my $foo = 'bar';
 ;;
 my %data;
 push @{ $data{$foo} }, qw(zero one two three);
 dd \%data;
 ;;
 print qq{'$data{$foo}[1]'};
"
{ bar => ["zero", "one", "two", "three"] }

'one'
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