package MyLib;

our $MyLibrarysGlobalCallStackInformation;

sub myfunc1
{
  local $MyLibrarysGlobalCallStackInformation = $somedata;

  myfunc2();
}

sub myfunc2
{
  # use $MyLibrarysGlobalCallStackInformation here
}

##</code><code>##

package MyLib;

sub myfunc1
{
  myfunc2($somedata);
}

sub myfunc2
{
  my ($somedata) = @_;
  # use $somedata here
}

##</code><code>##

package MyLib;

sub myfunc1
{
  my (@args) = @_;
  return myfunc2(@args, $somedata); #instead of goto &myfunc2
}

sub myfunc2
{
  my ($arg1, $arg2, $arg3, $somedata) = @_;
  if (defined $somedata) {
   .. # we got there from myfunc1
  }
}