You can accomplish what you want by

  substr($packet,0,1) = "X";
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I think that you are confusing perl with C. I attempted to do similar things when I first started perl programming.

In C, a string is an array of bytes (with a null byte as a terminator), so you can write:

char * packet = "abcdefg";
packet[0] = 'X';

/* packet now contains "Xbcdefg" */
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You can't do that in perl, because in a perl scalar variable can contain a string as a single item. It usually makes no sense to treat it as some sort of list type containing characters or bytes.

As other posters have said, if you want to change one character of a string, then you can use substr, but I suspect that is not what you are trying to do.

If you really want an array of characters, then you can declare one explicitly with something like:

@packet = ('a', 'b', 'c');
@packet = qw( a b c );
@packet = split //, "abc";
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(All three lines produce the same result)

What is it that you are trying to achieve? I think if you give us more detail, we can help you solve your actual problem rather than natively pointing out what is wrong with what you have done so far.

I think that you are confusing perl with C

Maybe, but PHP and Python support this syntax as well.

$packet =~ s/^./X/;
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A hand. use it, and all will become clear.

my $packet = "abcdefg";
substr $packet, 0, 1, "X";
print $packet;
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Normally I would hesitate to give this adivce becuase I do not like to seem snarky, but with this and your previous question I am sensing some very basic confusion about Perl and programming in general. I think a lot of benefit would be gained by some careful reading of an introductory Perl book or on line documents,

"Learning Perl" in particular comes to mind. and I am certain the other monks have wonderful lists of resources.

I hope this is helpful and wish you well in you coding