@_ = qw (opt pot top stoop stop pit ipt);

##</code><code>##

opst counted 1 times
oopst counted 1 times
opt counted 3 times
ipt counted 2 times

##</code><code>##

use strict;

my %h;

@_ = qw (opt pot top stoop stop pit ipt);
for ( @_ )
{
    my $last;
    $h{join "", grep 
    { 
        if ( $_ eq $last ) { "" } 
        else               { $last = $_; $_ } 
    } 
    sort split "", $_}++;
}

for ( keys %h )
{
    print "$_ counted $h{$_} times\n";
}

##</code><code>##

opst counted 2 times
opt counted 3 times
ipt counted 2 times