Interval sets provide for a concise solution. Here's a demonstration using choroba's data.

#! /usr/bin/perl -wl

use Set::IntSpan;

($",$/) = (',','');

my ($f1, $f2) = map [ m/(\S+)/g ], <DATA>;

while (my ($k, $v) = splice(@$f1, 0, 2)) {

    my @r = map Set::IntSpan->new($_)->I($v), @$f2;

    print "$k: @{[map $_->run_list, grep $_->size, @r]}";

}

__DATA__
a 11-23
b 33-39
c 40-45
d 48-58

1-34 35-39 40-42 43-49 51-59 62-90
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