The link above will find overlapping ranges. If you just want to list both .bed files in sorted order, then the following will do it.

#!/usr/bin/perl
use strict;
use warnings;
use 5.014;

@ARGV = qw/ 148N.txt 162N.txt 174N.txt 175N.txt /;

my @data = map {[split]}
           map {$_->[0]}
          sort {$a->[1] <=> $b->[1] || $a->[2] <=> $b->[2] || $a->[3] 
+<=> $b->[3]}
           map {[ $_, /\d+/g]} <>;

say "@$_" for @data;
[download]

C:\Old_Data\perlp>perl t6.pl
chr1 10 50
chr1 12 40
chr1 20 45
chr1 25 30
chr1 25 50
chr1 41 45
chr1 48 80
chr1 60 80
chr1 100 500
chr10 10 20
[download]