I get the same either way and no difference with Excel

#!perl
use strict;
use Statistics::Basic 'stddev';

my @data = (0.964, 0, 0, 0.94, 0.895,
0.915, 0.775, 0.868, 0, 0.796, 0.866,
0.819, 0, 0, 0, 0, 0.794, 0.806,
0.781, 0.807, 0.783);
print stddev(\@data)+0;
print "\n";
print stddev(@data)+0;
# 0.400791162022762
 
# excel 
# STDEVP 
# Calculates standard deviation based 
# on the entire population given as arguments.
# 0.400791162
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