perl doubt
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Definition
This function takes the leftmost element from the array specified and returns that, reducing the array by one element. When no array is specified, the array of arguments passed to the Perl script, $ARGV, is used if the context is not in a subroutine; otherwise, the array of arguments passed to the subroutine, @_, is used.
The return value is undefined if the array is empty.
So it looks like it's pulling the path out of the command line arguments