sub get_arg {
    shift =~ /="?([^="])/;
    $1;
}
[download]

or, in two steps

sub get_arg {
    my ($x) = shift =~ /="?([^="])/;
    $x =~ tr/"'//;
    $x;
}
[download]

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.