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perlpacktut: Remove some jargon #23251

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23 changes: 13 additions & 10 deletions pod/perlpacktut.pod
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Original file line number Diff line number Diff line change
Expand Up @@ -41,11 +41,10 @@ of these two functions.

To see how (un)packing works, we'll start with a simple template
code where the conversion is in low gear: between the contents of a byte
sequence and a string of hexadecimal digits. Let's use C<unpack>, since
this is likely to remind you of a dump program, or some desperate last
message unfortunate programs are wont to throw at you before they expire
into the wild blue yonder. Assuming that the variable C<$mem> holds a
sequence of bytes that we'd like to inspect without assuming anything
sequence and a string of hexadecimal digits. The example we've chosen
looks like a crash dump, and shows how C<unpack> can be used to make
sense of things like this. Assuming that the variable C<$mem> holds a
sequence of bytes that we'd like to inspect without assuming anything
about its meaning, we can write

my( $hex ) = unpack( 'H*', $mem );
Expand All @@ -58,17 +57,21 @@ corresponding to a byte:

What was in this chunk of memory? Numbers, characters, or a mixture of
both? Assuming that we're on a computer where ASCII (or some similar)
encoding is used: hexadecimal values in the range C<0x40> - C<0x5A>
encoding is used: hexadecimal values in the range C<0x41> - C<0x5A>
indicate an uppercase letter, and C<0x20> encodes a space. So we might
assume it is a piece of text, which some are able to read like a tabloid;
but others will have to get hold of an ASCII table and relive that
firstgrader feeling. Not caring too much about which way to read this,
assume it is a piece of ASCII text. We can verify that by doing

print unpack( 'A*', $mem), "\n"

A MAN A PLAN A CANAL PANAMA
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This is no different to:

print $mem, "\n";

I don't see how it adds anything


Going back to the original C<H*> for the purposes of this tutorial,
we note that C<unpack> with the template code C<H> converts the contents
of a sequence of bytes into the customary hexadecimal notation. Since
"a sequence of" is a pretty vague indication of quantity, C<H> has been
defined to convert just a single hexadecimal digit unless it is followed
by a repeat count. An asterisk for the repeat count means to use whatever
remains.
remains. That is also the case for the C<A*> above.

The inverse operation - packing byte contents from a string of hexadecimal
digits - is just as easily written. For instance:
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