In the spirit of TIMTOWTDI here is an atempt to get it into a one liner, for some definitions of one line anyway :)

perl -e'while(1){print"enter h/y:";$_=<>;next unless/^[hy]$/;($s,$m)=/
+h/?(yearly,2080):(hourly,1/2080);print"enter rate:";$_=<>;print"your 
+$s rate is ",$_*$m,$/}' 

# or expanding the same idea into a proper program

#!/usr/bin/perl
use strict;
use warnings;
my $hours=40*52; # are you mad ? 
while(1){
    print 'Do you wish to calculate yearly salary (y) or hourly rate?(
+h): ';
    chomp($_=<>);
    last unless $_;
    next unless/^[hy]$/;
    my @words=("yearly salary", "hourly rate");
    my ($ask, $say,$multiplier)=/y/?(1, 0, $hours):(0, 1, 1/$hours);
    print "Enter your $words[$ask]: ";
    $_=<>;
    print"your $words[$say] is ", $_*$multiplier, "\n\n"
}
[download]

Cheers,
R.