Brainf*ck has 8 operations: 
BF   equivalent in C
+    *p++
-    *p--
>    p++
<    p--
[    while (*p) {
]    }
.    putchar(*p)
,    *p = getchar();

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Using these, how does one figure out if X is less than Y? (Feel free to express you answer in Perl, but be sure you use nothing more than this operations.)
Updated 
sample BF code to put 50 in slot 0
+         add 1 to slot 0
>         move to slot 1
+++++++   add 7 to slot 1
[         while slot 1 is not 0
  <         move to slot 0
  +++++++   add 7 to slot 0
  >         move to slot 1
  -         subtract 1 from slot 1
]
<         move back to slot 0

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japhy -- Perl and Regex Hacker

In reply to Brainf*ck Question by japhy

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