#! perl -slw
use strict;
use Data::Dump qw[ pp ];
use 5.010;
use Time::HiRes qw[ time ];
use constant {
    GR => 1.6180339887498948482,
    ROOT5 => sqrt( 5 ),
};

sub fibCalc {
    int( GR ** $_[0] / ROOT5 + 0.5 );
}

my $start = time;
fibCalc( $_ ) for 1 .. 1474;
printf "calulating fibonacci( n ) for n := 1 to 1474 takes: %f seconds\n", 
    time() - $start;

__END__
C:\test>885839 1000
calulating fibonacci( n ) for n := 1 to 1474 takes: 0.001122 seconds