use Math::Fleximal;

my $number = '123456789012345678901234567890';
my $str = dec2alpha($number);
print "$str\n";
print alpha2dec($str), "\n";

# Turns a number from base 10 to base 62
sub dec2alpha {
  Math::Fleximal->new(
    shift, [0..9]
  )->change_flex(
    [0..9, 'a'..'z', 'A'..'Z']
  )->to_str();
}

# Turns a number from base 62 to base 10
sub alpha2dec {
  Math::Fleximal->new(
    shift, [0..9, 'a'..'z', 'A'..'Z']
  )->change_flex(
    [0..9]
  )->to_str();
}
__DATA__
Prints:

2AyLS9BKAMjjsWHR0
123456789012345678901234567890