Well I've tried this :

for ( 0..500000) {
push @aa, "abcdef"
}
print "waiting";
$t=<STDIN>
[download]

And the perl interpreter gobbles up 22MB. This:

print "waiting";
$t=<STDIN>
[download]

uses only 1.2MB. So I'd say the hash uses roughly 4MB for 100000 entries (40KB per line).