Do not set if TCP_NODELAY is not available

[dex4er]

Hi,

On Android with Termux and Perl 5.24.0:

u0_a168@localhost:~$ perl -MSocket=TCP_NODELAY -e TCP_NODELAY
Your vendor has not defined Socket macro TCP_NODELAY, used at -e line 1

Could you add some workaround, please?

[miyagawa]

You should not call eval in every request - instead you should do it once when importing Socket module and define it as a constant in the package.