a hash is a mapping from a string to a scalar. the symbol table is (simplified) a mapping from a string (the variable name) to the variable.

what you want to do is possible, but why bother with doing complicated things with the symbol table and even do no strict; when you can have a simple hash of hashes?

my @hashNames = qw(testA testB testC);
my $i = 0;
my %hoh;
foreach (@hashNames) {
  $hoh{$_}->{key} = $i;
}
# later
print $hoh{testA}->{key};
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see perldata, perllol