If you do have the unfortunate case of having the string not being interpolated then you could use the string version of eval() to get the desired result.

my $hr  = { foo => { bar => '/dev/null' } };
my $cmd_literal = 'ls $hr->{foo}->{bar}';
my $cmd = eval qq(return "$cmd_literal";);

print `$cmd`;

__output__

/dev/null
[download]

But the best option would be to have $cmd be interpolated rather than resorting to eval().
HTH

broquaint