rewraping data, preserving indent (as is important for example in yaml):

#!/usr/bin/perl

use strict;
use warnings;

sub rewrap {
    my ( $fh, $wrap_col ) = @_;
    $wrap_col ||= 72;

    my $indent = -1;
    my $width  = -1;
    my $indent_space;

    my $ensure_indent = sub {
        my ($line) = @_;
        return unless $indent < 0;
        $line =~ /^(\s+)/;
        $indent       = $1      ? length($1)    : 0;
        $indent_space = $indent ? ' ' x $indent : "";
        $width        = $wrap_col - $indent;
    };

    my $to_print = "";
    while ( my $line = <$fh> ) {
        chomp $line;
        $ensure_indent->($line);

        $line =~ s/^\s+|\s+$//g;

        # end wrapping on empty lines
        if ( !$line ) {
            if ($to_print) {
                print $indent_space, $to_print, "\n";
            }
            $to_print = "";
            print "\n";
            next;
        }

        $to_print .= $line;
        while ( length($to_print) > $width ) {
            my $segment = substr( $to_print, 0, $width );
            print $indent_space, $segment, "\n";
            $to_print = substr( $to_print, $width );
        }
    }
    if ($to_print) {
        print $indent_space, $to_print, "\n";
    }
}

rewrap( \*STDIN, $ARGV[0] );

Example of a file that is lines longer than desired:

$ cat bar.txt 
          00000001000000020000000300000004000000050000000600000007000000080000000900000010
          00000011000000120000001300000014000000150000001600000017000000180000001900000020
          00000021000000220000002300000024000000250000002600000027000000280000002900000030
          00000031000000320000003300000034000000350000003600000037000000380000003900000040
          00000041000000420000004300000044000000450000004600000047000000480000004900000050
          00000051000000520000005300000054000000550000005600000057000000580000005900000060
          00000061000000620000006300000064

Example of sending through the script:

$ cat bar.txt | ./rewrap.pl
          00000001000000020000000300000004000000050000000600000007000000
          08000000090000001000000011000000120000001300000014000000150000
          00160000001700000018000000190000002000000021000000220000002300
          00002400000025000000260000002700000028000000290000003000000031
          00000032000000330000003400000035000000360000003700000038000000
          39000000400000004100000042000000430000004400000045000000460000
          00470000004800000049000000500000005100000052000000530000005400
          00005500000056000000570000005800000059000000600000006100000062
          0000006300000064

Specifying a wrap-column other than the default:

$ cat bar.txt | ./rewrap.pl 66
          00000001000000020000000300000004000000050000000600000007
          00000008000000090000001000000011000000120000001300000014
          00000015000000160000001700000018000000190000002000000021
          00000022000000230000002400000025000000260000002700000028
          00000029000000300000003100000032000000330000003400000035
          00000036000000370000003800000039000000400000004100000042
          00000043000000440000004500000046000000470000004800000049
          00000050000000510000005200000053000000540000005500000056
          00000057000000580000005900000060000000610000006200000063
          00000064