$ cat test.txt 
one
two
three
$ part="C:00000092666270:53882159774"
$ echo $part
C:00000092666270:53882159774
$ perl -pse 'print qq{foo = [ "$bar" ]\n} if $. == 3' -- -bar="$part" test.txt
one
two
foo = [ "C:00000092666270:53882159774" ]
three
$ export part
$ perl -pe 'print qq{foo = [ "$ENV{part}" ]\n} if $. == 3' test.txt
one
two
foo = [ "C:00000092666270:53882159774" ]
three