untested psuedo-code

use strict; # To make sure you use the right package names.
package My_Wrapper;
sub My_get_data 
{ 
    local $x, $y, $z; # I had 'my', but [tilly] is right.
                      # Thats why I said, "I think." here.
    get_data( @_ );
    return ( $x, $y, $z );
}
package My_main
my ( $x, $y, $z ) = My_Wrapper::My_get_data;
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That's a stab in the dark. I'm tired and I don't feel like taking the time to construct your situation for testing. But I think that is the direction to go. My_Wrapper will collect ugly globals, but they shouldn't propogate to My_main.