its look my program it was looping wrongly / twice

Which loop? There is a huge loop within the display subroutine, and one in the main program.
If the one in the subroutine is wrong, then look at where you change $data:

@record = unpack $template, substr $data,0,$len,'';
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Maybe check $len?

If the loop in main, then that would indicate you are not hitting end-of-file when you expect, which implies the file has a different layout to the one you expect. Go back to the specification of the file layout and recheck your code.

Update: I just noticed you are using Switch. This has a range of strange side effects, and should not be used - use given/when, or a hased based despatch table instead. I can't say that Switch would cause your problems, but those are rather vague anyhow.