You assigned a array to a hash. This operation does a nice key - value kinda grouping of the array values. So your first re got a key and your second re got a value.

#!/usr/bin/perl
use strict;

my @array = (qr/^foo /, qr/bar$/);
print "@array\n";

my %hash = map {$_, 1} @array;
foreach (keys %hash) {
    print "$_\n";
}
[download]