The @ARGV array holds the parameters to the script. Subroutine parameters are retrieved from a different array: @_. See both in perlvar.

The first line of a subroutine usually looks like this:

    my @parameters = @_;
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or

    my ($x, $y) = @_;
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or even

    my $x = shift;
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shift is special: if you don't give it an argument, it shifts the first element from @ARGV in the main body, or the first element form @_ in a subroutine.