#!/usr/bin/perl 
                                                                                 
use strict; 
use warnings; 
no warnings 'numeric'; 
                                                                                 
my %subs = ( F => sub { ($_[0] - 32) * 5 / 9 }, 
             C => sub { ($_[0] * 9 / 5) + 32 } ); 
                                                                                 
my %scale = ( F => 'C', C => 'F' ); 
                                                                                 
if ($ARGV[0] =~ /([cf])\s*$/i and $subs{uc $1}) { 
  print "$ARGV[0] is ", $subs{uc $1}->($ARGV[0]),  
        "$scale{uc $1}\n"; 
} else { 
  print "Invalid input: @ARGV\n"; 
}