Here is a simple method. Note, the pid of the perl and ps processes will also show up if $user runs the program.

    #!/usr/bin/perl -w

    use strict;

    my $user  = 'root';
    my @procs = `ps -U $user`;

    shift @procs; # Omit title line

    my @pids = map { (split)[0] } @procs;
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--
John.