長さと分割数から範囲のリストを生成(Perl)

range.pl

#!/usr/bin/perl

# 長さと分割数から範囲のリストを生成します
#
# 例: 長さ100を5区間に
# $ range.pl 100 5
# 1       0       19                                                                                                                                                                                                 │
# 2       20      39                                                                                                                                                                                                 │
# 3       40      59                                                                                                                                                                                                 │
# 4       60      79                                                                                                                                                                                                 │
# 5       80      99

use strict;
use warnings;

use POSIX qw(floor ceil);
use File::Basename qw(basename);

# STDOUT,STDERRのバッファリング抑制
{ $| = 1; my $old = select(STDERR); $| = 1; select($old); }

my $SCRIPT = basename $0;
   
sub usage {
  print STDOUT "Usage: $SCRIPT LENGTH DIVISION\n";
}

unless (2 <= scalar @ARGV) {
  usage;
  exit 1;
}

my ($LENGTH, $DIVISION) = @ARGV;
unless ($LENGTH =~ /^\d+$/ && $DIVISION =~ /^\d+$/) {
  usage;
  exit 1;
}

my $WIDTH = ceil($LENGTH / $DIVISION);

my $END   = $LENGTH - 1;

my $cur = 0;
my $i   = 1;

do {
  my ($a, $b) = ($cur, $cur + $WIDTH -1);
  $b = $END if ($END < $b);
  print STDOUT "$i\t$a\t$b\n";
  $cur = $b + 1;
  $i++;
} while ($cur <= $END);