open(SRC, $0) or die("ack: $!");
my @lines = <SRC>;

## $line is declared *before* the braces
foreach my $line (@lines) {

  ## $w is declared within the condition, which is
  ## also before the braces
  if(my($w) = $line =~ /\b(\w+)\b/) {
    print "bareword found: $w\n";
  }

  print "\$w is: ", (defined $w ? $w : "undefined"), $/
    if $line eq $lines[$#lines];
}

print "\$line is: ", (defined $line ? $line : "undefined"), $/;

__output__

bareword found: open
bareword found: my
bareword found: foreach
bareword found: if
bareword found: print
bareword found: print
bareword found: if
bareword found: print
$w is: undefined
$line is: undefined