When you call a sub with parameters, those parameters arrive at the sub in the special array, @_. The usual practice is to copy the elements of that array immediately upon entering the sub. 

sub foo {
   my ( $x, $y ) = @_;
   # ...
}

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Sometimes that's done this way: 

sub foo {
    my $x = shift;
    my $y = shift;
    # ...
}

[download]

In that case, rather than just copying, shift is actually pulling items off the array (which are then copied).

In each of these, you can call foo( 'hello', 'world' ), and $x will take the value 'hello' while $y takes the value 'world'. If you call foo( $howdy, $doody ), the variables $howdy and $doody won't be visible inside foo, but their values will be in $x and $y.

In your particular case, you're trying to print $removeq immediately upon entering the sub without grabbing the arguments first. The cleanthefile sub doesn't see the $removeq of the caller directly. It just gets a copy via the @_ array. (The fact that it doesn't have a variable by that name is what the "Global symbol "$removeq" requires explicit package name" error is about.)

It actually does take a copy later, on this line: 

        my ( $sourcefile, $removeq )= @_;

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...but you're trying to print before that.

What I'd recommend, to start, is to get rid of that line, and put this at the very start of the sub: 

my ( $removeq ) = @_;

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At that point, I think the problem you may have is that $sourcefile doesn't have a value. I don't see where that value might come from, so I don't know how to advise you on how to fix that.

If you're interested in the gory details of sub calls in Perl, see perlsub.

In reply to Re^7: Program unsuspectingly dies with no reason why. by kyle
in thread Program unsuspectingly dies with no reason why. -FIXED! by misconfiguration

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