No, you are not doing what is written in the documentation. DrHyde is correct.

The documentation shows: $tar->extract_file( 'name/in/archive', 'name/i/want/to/give/it' );

Your code has this line though: $tar->extract_file($file, "C:/extract/$input"); # Extract $file to "C:/extract/libpst.tar.gz"

If you change it to the following it might work better: $tar->extract_file($file, "C:/extract"); # Extract $file to "C:/extract"