```{index} single: fibonacci; Math::GMP function ``` ```{index} single: Math::GMP::fibonacci; Perl function ``` # fibonacci Return the `$n`-th Fibonacci number. ## Synopsis ```perl my $f = Math::GMP::fibonacci(100); # 354224848179261915075 ``` Called as a function, not a method. `$n` is a plain Perl non-negative integer. `libgmp`'s recursive doubling algorithm handles indices in the millions in fractions of a second.