#!/usr/bin/perl

use strict;

my $source = "test data";

if ( @ARGV ) {
    $source = shift;
    open( DATA, '<', $source )
        or die "$source: $!\n Usage: $0 [data.file]\n";
}

my @inputs;
while (<DATA>) {
    chomp;
    push @inputs, $_;
}

# do some stuff with @inputs, as you see fit... e.g.

my $sum;
my $input_list;
for my $value ( @inputs ) {
    $sum += $value if ( $value =~ /^-?[\d.]+$/ );
    $input_list .= " $value";
}

printf( "There were %d values in '$source': %s\n The numeric sum is %f\n",
        scalar @inputs, $input_list, $sum );

__DATA__
5
10
non_numeric
15
20