I think you want something like:

#!/usr/bin/perl -wT
use strict;

my $filename = '/proc/uptime';

open(UTOP,$filename) or die "cant open '$filename': $!";
my $line = <UTOP>;              # grab a line from the file
close(UTOP);

my @fields = split(' ',$line);  # split the line into fields
print "Value = $fields[0]\n";   # print out the first field

=OUTPUT
Value = 13888666.52
[download]

and yes, that is my current uptime... 160 days and running.

-Blake