This is a problem with the shell, not with perl. If you use single quotes in the shell it won't interpolate. eg.

$ part="C:00000092666270:53882159774"
$ echo $part
C:00000092666270:53882159774
$ echo '$part'
$part
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Use double-quotes to interpolate or (easier) just unquote the variable when you want to use it. Better still, put it in the environment so perl can access it through %ENV.