Its origins, being non-commercial, fostered a strong "gift society" (as tilly once put it I think.) The result is that giving advice, help, instruction, and so forth are the social norm in this community.
The "gift culture" actually applies, as mentioned, not only perl, but hacker-dom in general, as talked about in the Hacker FAQ (How to Become A Hacker)
. Written by the maintainer of the Jargon File
, it's a very good read. Perl is more of a hacking language, which probably explains why its community is so giving.
elusion : http://matt.diephouse.com