I'm trying to make use of the pack/unpack pattern 'C/a*' but am encountering several sorts of weirdness.

If I do 

my $packed = pack 'C/a*', 'the quick brown fox';
print "'$packed'";

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I get '?the quick brown fox'. The string, prefixed with a 1-byte length.

And when I do

print unpack('C/a*', $packed);

I get the quick brown fox. The original string minus the length prefix. Great!

However, when I do 

my $data = unpack 'C/a*', $packed;
print "'$data'";

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I get 19 the length of the string? Ah, Context!. Scalar/versus list. So I tried: 

my @data = unpack 'C/a*', $packed;
print scalar @data, ':', join '|', @data;

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and got 1:the quick brown fox. The array has one element, and its the string not then length?

So then I tried 

my ($len, $val) = unpack 'C/a*', $packed;
print "$len:$val;";

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and got 

Use of uninitialized value in concatenation (.) or string at C:\test\t
+est.pl line 16.
the quick brown fox:;

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So, unpack with a template of 'C/a*' returns the length and not the string in a scalar context and a one element list consisting of just the string, but not the length in a list context.

So to get both pieces of information I have to call unpack twice? 

my $len = unpack 'C/a*', $packed;
my ($data) = unpack 'C/a*', $packed;

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Or just do the latter and use length.

Conclusion: This is, at the very least, unintuative, non-DWIM, perverse and undocumented, and quite possibly a bug?

Worthy of a perlbug?

Examine what is said, not who speaks.

The 7th Rule of perl club is -- pearl clubs are easily damaged. Use a diamond club instead.

In reply to unpack 'C/a*' and context weirdness by BrowserUk

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