Instead of:

my @results = `ps -ef`;
[download]

you could do:

my @results = `ps -fu $user`;
[download]

This should give you only your processes and eliminates one of your filters.

TO check if the parent process is a shell or not, check the command part of the process info, which should be the basename of your $SHELL value. If not, you would have to go for its parent until you find the real shell.

Also, I would use a hash instead of an array for the list of process hashrefs.

Anyway, here is some (untested) changes to your code:

#!/usr/bin/perl -w
use strict;
my $prog = (split "\/", $0)[-1];

die "Usage: $prog\n" if @ARGV;
my $user = getpwuid $<;
my @results = qx{/bin/ps -fu $user};
chomp @results;
shift @results; # remove header

my %listing;
for (@results) {
    if (m|^([\w\d]+) \s+
        (\d+) \s+
        (\d+) \s+
        (\d+) \s+
        ([\w\d:]+) \s+
        ([\w\d/?]+) \s+
        ([\w\d:]+) \s+
        (.*)$|x) {
        my $hashref;
        $$hashref{'uid'} = $1;
        $$hashref{'pid'} = $2;
        $$hashref{'ppid'} = $3;
        $$hashref{'c'} = $4;
        $$hashref{'stime'} = $5;
        $$hashref{'tty'} = $6;
        $$hashref{'time'} = $7;
        $$hashref{'cmd'} = $8;
        $listing{$pid} = $hashref;
    }
    else {
        warn "$prog: Could not process line! Line follows:\n$_\n";
        next
    }
}

my ($shell) = ($ENV{SHELL} =~ m{([^/]*)$}; # get the basename of the s
+hell
my $pid = $$;
my $ppid = $listing{$pid}->{ppid};
while ($listing{$ppid}->{cmd} !~ m/$shell$/;) {
    $pid = $ppid;
    $ppid = $listing{$pid}->{ppid};
}

# $ppid should have the current shell's pid

for my $pid (keys %listing) {
    kill 9, $pid
        unless $listing{$pid}->{cmd} =~ m/^-/ and $pid != $ppid;
}
[download]

/prakash