# alternately, you may want to push them onto @perschecked
for my $x ( 0 .. 2 ) {
    $perschecked[ $x ] = $files[ $x ] . ( $x + 1 );
}

##</code><code>##

for my $x ( 0 .. 2 ) {
    $files[ $x ] .= ( $x + 1 );
}