Echoing comments from stevieb, post some "working" code that shows the precision problem. This code doesn't do that for me.

#!/usr/bin/perl
use strict;
use Math::BigFloat;
Math::BigFloat->accuracy(20);
    
sub simulate_lifespan{
    my $r = Math::BigFloat->new($_[0]);
    my $org_muv = Math::BigFloat->new($_[1]);
    my $org_muy = Math::BigFloat->new($_[2]);
    my $scaler = Math::BigFloat->new($_[3]);
    my $ext_death = Math::BigFloat->new($_[4]);

    my $lifetime_fitness = Math::BigFloat->new(0);
    my $log_lifetime_fitness = $lifetime_fitness->copy();
    $log_lifetime_fitness ->blog();
    my @return_array = ($time, $log_lifetime_fitness, $mean_v, $mean_y
+);
    return \@return_array;
}

__END__
prints:
Global symbol "$time" requires explicit package name at C:\Projects_Pe
+rl\testing\junk.pl line 16.
Global symbol "$mean_v" requires explicit package name at C:\Projects_
+Perl\testing\junk.pl line 16.
Global symbol "$mean_y" requires explicit package name at C:\Projects_
+Perl\testing\junk.pl line 16.
Execution of C:\Projects_Perl\testing\junk.pl aborted due to compilati
+on errors.

Process completed with exit code 255
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