#!/usr/bin/env perl -l

use strict;
use warnings;

my @filenames = qw{
    MOLEC8-B040-OPT-FREQ2.gout
    MOLEC1-B001-OPT-FREQ2.gout
    MOLEC2-B010-OPT-FREQ2.gout
    MOLEC10-B002-OPT-FREQ2.gout
};

my $re = qr{^[^-]+-([^-]+)};

my @sorted = sort { ($b =~ /$re/)[0] cmp ($a =~ /$re/)[0] } @filenames;

print 'Original filenames:';
print for @filenames;

print 'Sorted filenames:';
print for @sorted;