The reason get_ids({'id_one','id_two','id_three'}) doesn't work is because it is taking each pair of values as a key/value pair. So that line is constructing a hash { id_one=>'id_two', id_three=>undef }.

If you were running with warnings enabled, you would be receiving a message Odd number of elements in hash assignment at... which would have given you a clue here

Without asking why you want to do this, though from what you've told us it seems bizaar:), you could do

get_ids( {id_one=>undef, id_two=>undef, id_three=>undef } );

However, if the idea is that you are going to return the hash to the caller with the values for the keys supplied filled in, it might be better to pass a ref to an anon. array of the values and then construct the hash internally like this.

sub get_ids {
    my %hash;
    @hash{@{shift()}} = undef;
    print "key:$_\n" for keys %hash;
    return \%hash;
}

# Call it this way
my $hashref = get_ids( [qw/id_one id_two id_three/] );
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If you run that, you'll get output

key:id_one
key:id_three
key:id_two
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