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

[download]

In reply to Re: Passing a BigFloat number through a subroutine by Marshall
in thread Passing a BigFloat number through a subroutine by pgnelson307

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.