From dankogai@dan.co.jp

This is possibly related to https://rt-archive.perl.org/perl6/Ticket/Display.html?id=127184 .
Run the code below​:

  #!/usr/bin/env perl6
  use v6;
  my $log2 = log(2);
  for 0..20 {
  say sprintf "%%.%dg​:\t%.{$_}g", $_, $log2;
  }

and you get​:

  %.0g​: 1
  %.1g​: 0.7
  %.2g​: 0.69
  %.3g​: 0.693
  %.4g​: 0.6931
  %.5g​: 0.69315
  %.6g​: 0.693147
  %.7g​: 0.6931472
  %.8g​: 0.69314718
  %.9g​: 0.693147181
  %.10g​: 0.6931471806
  %.11g​: 0.69314718056
  %.12g​: 0.69314718056
  %.13g​: 0.6931471805599
  %.14g​: 0.69314718055995
  %.15g​: 0.693147180559945
  %.16g​: 0.693147180559945
  %.17g​: 0.693147180559945
  %.18g​: 0.693147180559945
  %.19g​: 0.693147180559945
  %.20g​: 0.693147180559945

With perl5 version​:

  #!/usr/bin/env perl
  use v5.22;
  use warnings;
  my $log2 = log(2);
  for (0..20) {
  say sprintf "%%.%dg​:\t%.${_}g", $_, $log2;
  }

  %.0g​: 0.7
  %.1g​: 0.7
  %.2g​: 0.69
  %.3g​: 0.693
  %.4g​: 0.6931
  %.5g​: 0.69315
  %.6g​: 0.693147
  %.7g​: 0.6931472
  %.8g​: 0.69314718
  %.9g​: 0.693147181
  %.10g​: 0.6931471806
  %.11g​: 0.69314718056
  %.12g​: 0.69314718056
  %.13g​: 0.6931471805599
  %.14g​: 0.69314718055995
  %.15g​: 0.693147180559945
  %.16g​: 0.6931471805599453
  %.17g​: 0.69314718055994529
  %.18g​: 0.693147180559945286
  %.19g​: 0.6931471805599452862
  %.20g​: 0.69314718055994528623

Dan the Inaccurate Perl Monger