#!/usr/bin/env perl
use strict;
use warnings;
$^I = '.bak';
my $head_len = 5;
my $foot_len = 3;
while (<>) {
chomp;
print substr($_, $head_len, length($_) - $head_len - $foot_len), "\n";
}
####
$ ls -l pm_1076973.*
-rwxr-xr-x 1 ken staff 210 5 Mar 08:50 pm_1076973.pl
-rw-r--r-- 1 ken staff 87 5 Mar 08:46 pm_1076973.txt
##
##
$ cat pm_1076973.txt
12345... content ...123
12345... more content ...123
12345... even more content ...123
##
##
$ pm_1076973.pl pm_1076973.txt
##
##
$ ls -l pm_1076973.*
-rwxr-xr-x 1 ken staff 202 5 Mar 08:56 pm_1076973.pl
-rw-r--r-- 1 ken staff 63 5 Mar 08:56 pm_1076973.txt
-rw-r--r-- 1 ken staff 87 5 Mar 08:46 pm_1076973.txt.bak
##
##
$ cat pm_1076973.txt
... content ...
... more content ...
... even more content ...
##
##
$ cat pm_1076973.txt.bak
12345... content ...123
12345... more content ...123
12345... even more content ...123