[Foreigner]

ВиталийВ, Powershell устроит?

Код:

$mask1 = '[mask1]'
$mask2 = '[mask2]'
$mask3 = '[mask3]'

get-content 'C:\file.txt' | group {$_.split('.')[0]} | foreach {

	$group = $_.group
	$group[0..($group.count-2)] | foreach { $mask1 + $_ }
	$mask2 + $group[-1] + $mask3

} | set-content 'C:\file.txt'