Re: passing variables between subroutines

If your variable is a simple scalar, you can pass it to the sub as follows:

my $return = mailoff($myvar);

sub mailoff
{
     my $var = $_[0];
     #do stuff
     return $vartoreturn
}
[download]

If you want to pass arrays and hashes around, you can pass them as a list:

mailoff(@array);
sub mailoff
{
   my @array = @_;
}
..
mailoff(%hash)
sub mailoff
{
  my %hash = @_;
}
[download]

But a) you can only pass one array or hash that way, and b) it's a copy, not the original, so changes won't be seen in your main program (that's true in the first example as well, hence the return variable).

Alternatively, you could look at perlref, and pass references around. There's some simple introduction to that technique in Why use references?.

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John Brunner, "The Shockwave Rider".

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Re^2: passing variables between subroutines by Grygonos (Chaplain) on Jan 16, 2006 at 15:51 UTC
It's best to avoid passing non-scalars around that way. I think you're generally better served by passing the references `my @test = (1,2); my @test2 = (3,4); foo(\@test,\@test2); sub foo { my ($array,$array2) = @_; print $_ ."\n" for(@{$array}); print $_ ."\n" for(@{$array2}); }` [download] Grygonos	[reply] [d/l]
Re^3: passing variables between subroutines by revdiablo (Prior) on Jan 16, 2006 at 18:57 UTC
It's best to avoid passing non-scalars around that way I have to say I disagree with that as stated. Certainly, there are many cases where passing a reference is preferable, but it depends on the situation. My default is to pass a simple list and switch to passing references when there's a clear need. I'd even go so far as to say it's best to err on the side of not making references when they're not needed.	[reply]
Re^4: passing variables between subroutines by Grygonos (Chaplain) on Jan 17, 2006 at 19:14 UTC
So, can you give me an example of when it would not be a good idea to pass a reference to a non-scalar? I'm asking in earnest. I truly want to know. Grygonos	[reply]
Re^3: passing variables between subroutines by blazar (Canon) on Jan 17, 2006 at 10:45 UTC
It's best to avoid passing non-scalars around that way. I think you're generally better served by passing the references First of all the person you're replying to already pointed out that possibility in his post. Said this, I beg to differ with your claim and to stress that it is actually a possibility, albeit one that -as he also pointed out- turns into a necessity under certain circumstances. But generally speaking there are situations in which passing a reference is preferrable and others in which it is preferrable not to. However, stating a claim like that may easily turn into cargo culting the use of referencing and dereferencing all the time, which has already been observed around.	[reply]


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