How can I process options using Perl in -n or -p mode?

Question

When running perl -n or perl -p, each command line argument is taken as a file to be opened and processed line by line. If you want to pass command

Answer 1

Here is a short example program (name it t.pl), how you can do it:

#!/bin/perl
use Getopt::Std;

BEGIN {
  my %opts;
  getopts('p', \%opts);
  $prefix = defined($opts{'p'}) ? 'prefix -> ' : '';
}

print $prefix, $_;

Call it like that:

perl -n t.pl file1 file2 file3

or (will add a prefix to every line):

perl -n t.pl -p file1 file2 file3