sub stack_depth() {
  my $depth = 1;
  $depth++ while defined caller($depth);
  --$depth;
}

##</code><code>##

#!/usr/bin/perl -wl
use strict;

sub stack_depth() {
  my $depth = 1;
  $depth++ while defined caller($depth);
  --$depth;
}
sub test1 { print stack_depth;test2() } # should be 1
sub test2 { print stack_depth;test3() } # should be 2
sub test3 { print stack_depth } # should be 3

print stack_depth; # what's our stack depth here? should be 0
test1();
__END__
outputs:
0
1
2
3