G'day Ostra,

"my program inputs values from a text file and stores them in an array called @nums. Is there an alternative code that can accomplish the same task?"

Tie::File does exactly that, e.g.

tie my @nums, 'Tie::File', $filename;
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List::Util has functions to find the minimum and maximum values:

min(@nums);
max(@nums);
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Given this file:

$ cat pm_num_list.txt
123
12e3
12e-3
-12e3
-123
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This code:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

use List::Util qw{min max};
use Tie::File;

tie my @nums, 'Tie::File', 'pm_num_list.txt';

print 'Min: ', min(@nums), "\n";
print 'Max: ', max(@nums), "\n";

untie @nums;
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Produces this output:

Min: -12e3
Max: 12e3
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You've been shown a few alternative methods for achieving this task. If efficiency is of concern to you, use Benchmark to compare them.

Here's links to the three pragmata I used: strict, warnings and autodie. strict and warnings are recommended for all your programs; autodie for code involving I/O (and a few other cases: check the doco).