```{index} single: nan; POSIX function ``` ```{index} single: POSIX::nan; Perl function ``` # nan Build a quiet NaN, optionally with a payload string. ## Synopsis ```perl my $q = POSIX::nan(); # quiet NaN my $p = POSIX::nan("0x42"); # NaN with payload where supported ``` ## Edge cases - An empty or missing argument yields a plain quiet NaN. - Payload strings the C library cannot parse fall back to a plain quiet NaN silently. ## Differences from upstream Fully compatible with upstream POSIX.