$b->doSomething($f);

package Blah;

sub doSomething
{
    my $self = shift;
    my ($f) = @_;

    $f->methodX();
}
[download]

The real question is how do I use a variable in one scope within another scope. The answer is you pass it. This isn't an OO question, it's a scoping question. It's also a pretty basic question.

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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.