# [at the top, before subroutine definitions and code]
my %my_vars;
# [...]

sub call_variables {
  #pick up a string I've passed from previous program via 'spec_vars'
  my $spec_vars = param('spec_vars');
  @my_vars{qw/one two three four five/} = split /~/, $spec_vars;
}

##</code><code>##

# [at the top, before subroutine definitions and code]
my ($one, $two, $three, $four, $five);
# [...]

sub call_variables {
  #pick up a string I've passed from previous program via 'spec_vars'
  my $spec_vars = param('spec_vars');
  ($one, $two, $three, $four, $five) = split /~/, $spec_vars;
}