my @fields = ( split /\s+/ ); # need to hold on to all fields for later
my( $index, $label ) = @fields[4, -1]; # this is an array slice
####
use 5.010;
given( $label ) {
when ( 'A' ) { $fields[ -2 ] = $x; }
when ( 'B' ) { $fields[ -2 ] = $y; }
default { say "OOPS! bad label"; }
}
####
say join "\t", @fields; # separates fields with TAB