#!perl -p
use strict;
use warnings;
#Usage: perl script.pl boiler.txt >outfile.txt
BEGIN{
    use vars qw( %hash $pattern );
    %hash = (
        FIRST_NAME => 'James',
        COMPANY    => 'SoftLayer',
    );
    $pattern = join '|', keys %hash;
}

s/\$($pattern)/$hash{$1}/ge;