#!/usr/bin/perl -w
use strict;

my $line;

while( (print "parameter to calculate?:"), 
       ($line=<STDIN>), $line !~ /^\s*q(uit)?\s*$/i)
{    
    next if $line =~ /^\s*$/; #blank line => simple re-prompt
    
    if ($line =~ /^\s*(resistance|R)\s*$/i)
    {
       print "sub to calculate resistance\n";    
    }
    elsif ($line =~ /^\s*(voltage|V)\s*$/i)
    {
       print "sub to calculate voltage\n";
    }
    elsif ($line =~ /^\s*(current|I)\s*$/i)
    {
       print "sub to calculate current\n";
    }
    else
    {
       print "illegal entry!\n";
    }   
}