#!/usr/bin/env perl
 
use 5.010;
use warnings;
 
my @times = map { /^(?:top - (..:..:..))/ } <DATA>;
 
say for @times;
 
__DATA__
top - 00:35:18 up
top - 01:23:45 other junk
completely different format altogether
not - 01:23:45 can't fool me!
top - 02:35:46
top - 03:46:07