# If able to delete the stuff(.*) between the beginning
# of the line(^) and the word 'alias' and one-or-more spaces(\s+)
# found after that ...
if (s/^.*?alias\s+//)
{
     # Extract the 1st, 5th and 7th "words"
     my ($varalias, $varsource, $vartarget)
           = (split(' '))[1,5,7];

     # Then whatever...
}