How to capture and save warnings in Perl

  #!/usr/bin/perl
  use strict;
  use warnings;

  local $SIG{__WARN__} = sub {
    my $message = shift;
    logger('warning', $message);
  };

  my $counter;
  count();
  print "$counter\n";
  sub count {
    $counter = $counter + 42;
  }


  sub logger {
    my ($level, $msg) = @_;
    if (open my $out, '>>', 'log.txt') {
        chomp $msg;
        print $out "$level - $msg\n";
    }
  }