#! /opt/local/bin/perl -w

# I recommend the strict pragma if you are new to perl
use strict;

# you could get the data you provided into an array in any
# number of ways.
my @data = ("1234-5678 12 .345678", "1234-5678 90 .123456");
my $sum;

foreach (@data) {
    # puts each piece of information into its own variable
    # in case you need to use them for something.
    # you could push them into arrays to keep track of them
    my ($user_id, $proc_id, $time) = split();

    # adds the time from the current line to the running
    # total of time values
    $sum += $time;
}

# divides the total times by the total number of times 
# (the index of the last element in the array + 1)
my $average = $sum/($#data + 1);

print $average;