Small problem. You may want to clear out the leading \b's after the while statement. Like many others on this thread, you've been bitten by the terminal's evaluation of \b.

#!/usr/bin/perl -l

$s = "\bt\b\bhello";

sub smack {
  $a = $s;
  $a =~ s/^\cH+//;
  1 while ($a =~ s/[^\cH]\cH//g);
  $a;
}

sub othersmack {
  $a = $s;
  1 while ($a =~ s/[^\cH]\cH//g);
  $a =~ s/^\cH+//;
  $a;
}

print smack();
print othermack();

print "smack correct" unless grep {ord==ord"\b"} split//,smack();
print "othersmack correct" unless grep {ord==ord"\b"} split//,othersma
+ck();
__END__
output:
hello
hello
othersmack correct
[download]

However, getting rid of the alternation is a good bit quicker. =)