Don't use tie. Since 5.8.0, you can create a file handle that reads from/writes to a scalar.

my $data = '...';
open(my $fh, '<', \$data) or die;
sub_that_needs_file_handle($fh);
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Before 5.8, IO::Scalar and IO::String provide the functionality (although not as well) by using tie

Neither tie nor this method produce a real (system) file handle, so they won't work where a real file handle is needed. For example, you can't use them to capture the output of a child process. (See IPC::Run for a solution in that particular case.)