#! perl -slw
use strict;

our $N //= 2;
our $M //= 1e6;

my( $step, $s, @ranges ) = ( int $M / $N, 0 );
push( @ranges, [ $s, $s+$step -1] ), $s+=$step for 1 ..$N;
$ranges[ -1][1] = $M;

printf "%2d : from %7d to %7d (%7d)\n",
    $_, @{ $ranges[ $_ ] },
    $ranges[ $_ ][ 1 ] - $ranges[ $_ ][ 0 ] + 1
    for 0 .. $#ranges;

__END__
[15:43:18.51] C:\test>ranges -N=1 -M=9999997
 0 : from       0 to 9999997 (9999998)

[15:43:29.03] C:\test>ranges -N=2 -M=9999997
 0 : from       0 to 4999997 (4999998)
 1 : from 4999998 to 9999997 (5000000)

[15:43:34.61] C:\test>ranges -N=3 -M=9999997
 0 : from       0 to 3333331 (3333332)
 1 : from 3333332 to 6666663 (3333332)
 2 : from 6666664 to 9999997 (3333334)

[15:43:47.64] C:\test>ranges -N=4 -M=9999997
 0 : from       0 to 2499998 (2499999)
 1 : from 2499999 to 4999997 (2499999)
 2 : from 4999998 to 7499996 (2499999)
 3 : from 7499997 to 9999997 (2500001)

[15:43:57.34] C:\test>ranges -N=5 -M=9999997
 0 : from       0 to 1999998 (1999999)
 1 : from 1999999 to 3999997 (1999999)
 2 : from 3999998 to 5999996 (1999999)
 3 : from 5999997 to 7999995 (1999999)
 4 : from 7999996 to 9999997 (2000002)