This sound like a home work, you should show us what did you try before

I hope you can understand next code, which do what do you want. See split,perlre, and substr if you need help reading it.

#!/usr/bin/perl
use strict;
use warnings;

my $range="0-2,6-10,13,15";
my $test="this is a test with more than 15 characters";

for my $r (split (",",$range))
{
    if ($r =~ /^(\d+)(-(\d+))?$/)
    {
        my $first=$1;
        my $length=1;
        if (defined ($3))
        {
            $length=$3-$1+1;
        }

        print "$r - ", substr ($test, $first,$length),"\n";
    }
}
[download]

Updated: For fun,see this example for use regex "...(..)..(..).." style (no substr needed). For "x" usage see Multiplicative Operators:

#!/usr/bin/perl
use strict;
use warnings;

my $range="0-2,6-10,13,15";
my @range=split(",",$range);
my $test="this is a test with more than 15 characters";

my $last=0;
my $regex="";
for (@range)
{
    if (/^(\d+)(-(\d+))?$/)
    {
        my $first=$1;
        my $length=1;

        if ($last lt $first)
        {
            $regex.="."x($last-$first);
        }
        $last=$first;
        if (defined ($3))
        {
            $length=$3-$1+1; $last=$3;
        }
        $regex.="(".("."x$length).")";
    }
}

my @matches = $test =~ /$regex/;

my $n=0;
for (@matches)
{
    print ++$n." ($range[$n-1]): \"" ."$_","\"\n";
}
[download]