convert ascii to binary, or binary to ascii

ascii_binary_convert.pl

#!/usr/bin/perl

use strict;
use warnings;

## one liner
# perl -ne 'print unpack("H*", $_)' < ascii > binary
# perl -ne 'print pack("H*", $_)'   < binary > ascii

my $mode = shift || help(); 

if (lc $mode eq "a2b") {
  while (<>) {
    print unpack("H*", $_);
  }
}
elsif (lc $mode eq "b2a") {
  while (<>) {
    print pack("H*", $_);
  }
}
else {
  help();
}

sub help {
  die 
  "Usage:
   ascii to binary: $0 a2b < ascii > binary
   binary to ascii: $0 b2a < binary > ascii\n";
}