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Re: what is the translation?

by BrowserUk (Pope)
on Jul 20, 2011 at 03:23 UTC ( #915571=note: print w/replies, xml ) Need Help??

in reply to what is the translation?

What is the tr/!-~/P-~!-O/ doing?

tr is perl's transliteration function.

It translates the characters in the string it is applied to, according to the two tables of characters given as its arguments.

For $string =~ tr/123/ABC/, it would change any and all occurrences of the characters '1','2', or '3', for the characters 'A', 'B', and 'C' respectively. Ie. If $string contained "a1b2c3c3b2a1", after the above code it would then contain "aAbBcCcCbBaA".

In your example, the first list is specified as: !-~ which is a short-hand notation meaning all the characters between '!' and '~', That is all the visible characters in the (7-bit) ASCII character set. Eg:

!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdef +ghijklmnopqrstuvwxyz{|}~

The second list, P-~!-O specifies the same characters, but in a different order, as two ranges. 'P' through '~' and '!' through 'O'. Effectively,

PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~!"#$%&'()*+,-./01234567 +89:;<=>?@ABCDEFGHIJKLMNO

The effect of these tables is that '!' will be translated to 'P' (and 'P' will become '!'); '"' will become 'Q' (and 'Q' becomes '"') and so on.

This is a reversible (obfuscation) process similar to ROT13. Effectively "ROT47".

However, why this is being applied to the input data, your guess is as good as mine. Probably better :)

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

Replies are listed 'Best First'.
Re^2: what is the translation?
by Albannach (Prior) on Jul 20, 2011 at 04:35 UTC
Re^2: what is the translation?
by roadtest (Sexton) on Jul 20, 2011 at 13:17 UTC
    Awesome! Thanks for your reply!

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