The hard way. :-)

Seriously, there may be easier solutions, (Set::IntSpan).

This way involves the vec function. 

#!/usr/bin/perl
use strict;
use warnings;
use List::Util qw/ min max /;

my @range = ([5,15], [2, 20]);

my $min = min map {$_->[0]} @range;
my $max = max map {$_->[1]} @range;

my @vec = ("") x @range;

for my $i (0 .. $#vec) {
    vec($vec[$i], $_, 1) = 1 for $range[$i][0] .. $range[$i][1];    
}

my $overlap = shift @vec;
$overlap &= $vec[ $_ ] for 0 .. $#vec;

my $count;
for my $offset ($min .. $max) {
    ++$count if vec($overlap, $offset, 1) == 1;
}

print $count;

[download]
And a thank you for this solution from another post by BrowserUK.

In reply to Re: Calculate overlap between 2 ranges of numbers by Cristoforo
in thread Calculate overlap between 2 ranges of numbers by Anonymous Monk

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