Use a signal handler (perlipc).

use strict;
use warnings;

my $max;

#-- set a signal handler
$SIG{INT} = sub {
  print "Max: $max -- now leaving...\n";
  exit 1;
};



#-- main
while (<>) {
  # do something that updates $max
}

print "Max: $max (finally)\n";

#-- normal termination (exit 0)
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Why not print "Value so far: $maxVal\r" unless $. % 250; inside your loop?

With the \r it will overwrite the previous text rather than scrolling madly, and give you a continual update. The $. % 250 keeps it from spending all its time printing. Adjust the variable and value depending on what you are looping over and how fast the loop spins.

I decided to write to a log interval at interval. Seems to be working splendidly. :)
I love it when a program comes together - jdhannibal

You might also consider keeping track of the max value encountered so far, replacing it when a higher max value is found. When this event happens, print a message saying "A new max value of $MAX was found..."

I would think that this would quickly stop reporting to the screen.

Take a small data set and process that and see what that does.