#!/usr/bin/perl --
use strict; use warnings;
my @list = ( qw{
bigBoy bigbang bigboy x10y x9y x11y 
1.01   1.3   1.02   1.2
x1.1y x1.01y x2.3y x2.1y } );

print join "\n", 
  map { $$_[0] }
  sort { $$a[1] cmp $$b[1] }
  map {
    my $f = $_;
    $f =~ s/(\d+)/sprintf '%06d',$1/ge;
    [ $_, lc $f ]
  } @list;
__END__
1.01
1.02
1.2
1.3
bigbang
bigBoy
bigboy
x1.1y
x1.01y
x2.1y
x2.3y
x9y
x10y
x11y