#!/usr/bin/perl

# http://perlmonks.org/?node_id=1206433

use strict;
use warnings;
use List::Util 'shuffle';
use Data::Dump 'pp';

my @before = shuffle qw( namem1100.111 namem0900.111 namem0010.111
  namep0000.111 namep0800.111 namep9999.111 );
pp \@before;

my @after = sort {
  $a =~ s/.*([pm]\d+).*/$1/r =~ tr/pm/+-/r <=>
  $b =~ s/.*([pm]\d+).*/$1/r =~ tr/pm/+-/r
  } @before;
pp \@after;
[download]

Outputs:

[
  "namem0900.111",
  "namep9999.111",
  "namem1100.111",
  "namep0800.111",
  "namep0000.111",
  "namem0010.111",
]
[
  "namem1100.111",
  "namem0900.111",
  "namem0010.111",
  "namep0000.111",
  "namep0800.111",
  "namep9999.111",
]
[download]