Here's a little more precise version of the question using the code I'm currently grappling with.

#!/usr/bin/perl -w
use strict;
 
## usage information
# $0 UPSNAME HOSTNAME DATAPOINT
#   where DATAPOINT can be any of
#      utility - the number VAC utility power is providing
#      loadpct - the percentage of the maximum load
#      battpct - percent of total battery charge available
#      runtime - approx. number of minutes of battery life
 
my $lookfor = $ARGV[2];
 
my @upsinfo = (`/usr/local/bin/upsc $ARGV[0]\@$ARGV[1]`);
my ($junk, $utility) = split /\s+/, $upsinfo[10];
my ($kunk, $loadpct) = split /\s+/, $upsinfo[14];
my ($lunk, $battpct) = split /\s+/, $upsinfo[21];
my ($munk, $runtime) = split /\s+/, $upsinfo[23];
 
if ($lookfor) {
        print $$lookfor;
} else {
        print "utility is $utility\n";
        print "loadpct is $loadpct\n";
        print "battpct is $battpct\n";
        print "runtime is $runtime\n";
};
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Why do I get the error:
Can't use string ("loadpct") as a SCALAR ref while "strict refs" in use... line 20 ?

Now, Page 58 of the Camel book (v3) says that $bert and ${ some_expression() } are the same, where some_expression() 'returns a reference to variable $bert (or even the string, "bert")'

I know that references are a concept around which my grasp is not firm, perhaps I've got it all mistaken. Please someone show me how to understand this problem.

Apologies if this is covered somewhere but I have not found it, a link and an RTFM is a generous answer.

By the way, this $0 is what I'm cobbling together to use NUT the Network UPS Tools and MRTG to chart the usage and performance of my UPSes over time.