#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11137734
use warnings;

my $inputfile = <<END;
[0..1]
[2..4]
9
[5..8]
END

open my $fh, '<', \$inputfile or die; # FIXME to your file
local $/;

my @sets = map { /\[(\d+)\.\.(\d+)\]/ ? $1 .. $2 : $_ } split ' ', <$fh>;

use Data::Dump 'dd'; dd \@sets;

##</code><code>##

[0 .. 4, 9, 5 .. 8]