Impossible. You're asking to do something that's the very definition of looping without using a loop. What do you actually want?

At university I learned that loops can be replaced by recursivity. So the simple code below fulfills the requirements of the OP (one line, no loop) ... but maybe isn't what he wants. ;-)

However this statement stems from a course of theoretical computer science. Don't use the code below in a productive environment. It is slower and takes much more resources than the other, straightforward solutions presented in this thread!

You have been warned! Rata 

use strict;
use warnings;

my @x = qw ( a b c d e ff ggg hhhh iiii );
my %y;

# Tata!!! Here comes the requested line of code:

noLoop(); sub noLoop { $y{pop(@x)} = 1; noLoop() if (scalar(@x)); }  #
+ btw.: using global vars in subs is usually bad style ;-)

print keys(%y), "\n";
exit 0;

[download]

In reply to Re^2: use array for hash-keys without loop by Ratazong
in thread use array for hash-keys without loop by piccard

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