Attempt at eliminating a global variable

wfsp has asked for the wisdom of the Perl Monks concerning the following question:

I have a sub that calls another sub.
I would like to have the called sub manipulate an array declared in the calling sub.
Below is a simplifed example of what I'm trying to do. The actual code I'm working on is a tk script.

This seems to be very expensive.

#! perl

use warnings;
use strict;

scope_test();

sub scope_test{
  my @data_in = <DATA>;
  my @data_out;
  for (0..$#data_in){
    @data_out = call_back($data_in[$_], @data_out);
  }
  print "$_" for @data_out;
}

sub call_back{
  my $element = shift;
  my @data_out = @_;
  push @data_out, $element;
  return @data_out;
}
  
__DATA__
line one
line two
line three
[download]

Comment on Attempt at eliminating a global variable Download Code

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Re: Attempt at eliminating a global variable by ikegami (Patriarch) on Jan 18, 2005 at 18:56 UTC
Pass a reference to the array: `call_back(\@data_out, $data_in[$_]); sub call_back{ my ($data_out, $element) = @_; push @$data_out, $element; }` [download] Alternate syntax: `call_back(\@data_out, $data_in[$_]); sub call_back{ our @data_out; local *data_out = $_[0]; my $element = $_[1]; push @data_out, $element; }` [download]	[reply] [d/l] [select]
Re^2: Attempt at eliminating a global variable by wfsp (Abbot) on Jan 18, 2005 at 19:09 UTC
Many thanks ikegami. Much neater too!	[reply]
Re^3: Attempt at eliminating a global variable by ikegami (Patriarch) on Jan 18, 2005 at 19:53 UTC
btw, `sub scope_test{ my @data_in = <DATA>; my @data_out; for (0..$#data_in){ call_back(\@data_out, $data_in[$_]); } print "$_" for @data_out; }` [download] can be simplified to `sub scope_test{ my @data_out; while (<DATA>) { call_back(\@data_out, $_); } print "$_" for @data_out; }` [download] or even `sub scope_test{ my @data_out; call_back(\@data_out, $_) while (<DATA>); print "$_" for @data_out; }` [download]	[reply] [d/l] [select]