Everyone known why print (1+1)*2; doesn't work as newbies might expect. But there's a simple rule to understand it: if it looks like a funtion call then it is a function call.

But I came across another example today: 

sub uniq
{
    local $_;
    my %seen;
    return grep { !$seen{$_}++ } @_;
}

print uniq 0,0,1,2;         # good: prints 0,1,2
print sort uniq 0,0,1,2;    # bad:  prints 0,0,1,2

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It appears that the sort function is seeing "uniq" as the code block that defines sort critera. OK, I thought, lets make it "look like a function call": 
print sort uniq(0,0,1,2);

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But nope, this still prints "0,0,1,2". To make it work I need to resort to: 
print sort grep {1} uniq 0,0,1,2;

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or some similar intusive builtin.

This example probably just scratches the surface of some parser logic that I haven't correctly groked. Why doesn't the "if it looks like a function" rule work in this case? If a builtin like "grep" (or "map") isn't treated as a sort-criteria code block, then how do I define my own subroutines that similarly are not sort-critera?

--Dave
Opinions my own; statements of fact may be in error.

In reply to When is a function call not a function call by dpuu

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