#!/usr/bin/perl -w
use strict;
# test on a string with just hours
my $uptime = '  9:12pm  up  2:13,  5 users,  load average: 0.84, 0.62, 1.03';

if( $uptime =~ /up\s+((\d+) days,\s+)?(\S+),/ ) {
    my ($dayup,$timeup) = ( $2,$3); # $1 is the first enclosing parens which we don't want
    print "timeup is ", defined $dayup ? " $dayup days and " : '', "$timeup hours\n";
}
# test again on a string with days
$uptime = "6:37PM up 4 days, 2:05, 2 users, load averages: 1.99, 1.65, 1.47";

if( $uptime =~ /up\s+((\d+) days,\s+)?(\S+),/ ) {
    my ($dayup,$timeup) = ( $2,$3); # $1 is the first enclosing parens which we don't want
    print "timeup is ", defined $dayup ? " $dayup days and " : '', "$timeup hours\n";
}