zen% cat t0
#!/usr/bin/perl -w
for (my $i = 0; $i < 2; $i++) {
  my $j = $i + 1;
 retry:
  warn "i: $i j: $j\n";
  if ($i < $j) {
    $j--;
    goto retry;
  }
}
zen% /opt/perl-5.8.0/bin/perl t0
i: 0 j: 1
i: 0 j: 0
i: 1 j: 2
Use of uninitialized value in concatenation (.) or string at t0 line 4.
i: 1 j: 
Use of uninitialized value in numeric lt (<) at t0 line 6.
Segmentation fault (core dumped)
zen% /opt/perl-5.8.1/bin/perl t0
i: 0 j: 1
i: 0 j: 0
i: 1 j: 2
i: 1 j: 1
zen%