You've given minimal information in your script, but it sounds like your hitting the swapper.

You neglect to mention how much memory is is use when the slow-down occurs, which is probably as important as the cpu utilisation. The "Physical Memory" and "Commit Charge" figures from the Perfromance tab of the Task Manager are your best indicators.

Alternatively, if you have Win32::API::Prototype installed, you could use this script to log memory use along side your ticker, and get an indication of the memory used -v- performance.

#! perl slw
use strict;
use Win32::API::Prototype;

my $memoryStatus = AllocMemory( 32 );
ApiLink( 'Kernel32', 'GlobalMemoryStatus', 'P', 'V' );

GlobalMemoryStatus( $memoryStatus );
my @keys = qw[
    length PercentageLoad
    TotalPhysical AvailablePhysical
    TotalPaged AvailablePaged
    TotalVirtualMemory AvailableVirtualMemory
];

my %mStatus;
@mStatus{ @keys } = unpack 'V8', $memoryStatus;

printf '%30s : %.2f ', $/,
    $_, $mStatus{ $_ } / 2**20
    for @keys[ 1 .. $#keys ];

__END__
P:\test>gMem
                PercentageLoad : 0.00
                 TotalPhysical : 510.98
             AvailablePhysical : 360.27
                    TotalPaged : 1250.05
                AvailablePaged : 908.16
            TotalVirtualMemory : 2047.88
        AvailableVirtualMemory : 2018.61
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