testing testing... perl question

[Jonathan McKeown]

On Monday 13 August 2007 12:31, Aidan Samuel wrote:
> Hello everyone, I'm new here.
>
> Is it ok to ask a perl question?
>
> perl -e '@a = (1..5); print sort $a <=> $b, @a;'
> 012345
>
> perl -e '@a = (1..5); print sort {$a <=> $b} @a;'
> 12345
>
> When using map and grep I tend to leave off the curly braces and just
> use a comma, but if I try this with sort, I get these odd results.

It's clearer what's happening when you look at:

perl -le '$, = " "; $b = 12; print sort $a <=> $b, (1,2,10,11,3)'
-1 1 10 11 2 3

sort in this case (and in your first example) doesn't have a block or 
subroutine name or reference (the bit in {} in your second example), so it 
does the default lexical sort of a six-item list: the value of $a <=> $b 
(which is -1 because $a (undef) is less than $b (12)), and the strings 1, 2, 
10, 11, and 3.

In your first example $a and $b were both undef so they compared equal, giving 
you the zero, and for single digits numeric and lexical sorts give the same 
result.

HTH
Jonathan