use warnings;
use strict;

my @array =
  (
  'foo bar quux bam',
  'foi bir quix bim',
  'foe ber quex bem',
  'foa bor quax bom',
  );

my $inst1 = '4 A -4 C -4 B 2 D';
my @result1;
my @inserts;

$inst1 =~ /[\d+-]+(?: \w ([\d+-]+)(?{push @inserts, $1}))*/g;

for my $line (@array)
  {
  my $index = 0;
  $line =~ s/\b /' '.$inserts[$index++].' '/eg;
  push @result1, $line;
  }

print join "\n", @result1;