#!/usr/bin/perl -w
use strict;

my $words='test Buffy testament Anya tot Willow tesseract
 Faith tent';
$words =~ s/\b(t[^t]+t)\b/$1 eq "test" ? $1  : ''/ge; 
print $words;
# prints 'test Buffy testament Anya  Willow  Faith';

##</code><code>##

$words =~ s/\b(t[^t]+t)\b/
           my $temp = $1;
           if($temp eq 'test'){
             $temp
           }else{
             ''
           }/xge; 

##</code><code>##

($_='kkvvttuubbooppuuiiffssqqffssmmiibbddllffss')
 =~y~b-v~a-z~s;                             print