use strict;
use warnings;

my @grabArray;

while (my $current_line = <DATA>) {
      next if $current_line !~ /Grab this\s+'([^']+)'/;

      push @grabArray, $1;
}

print join "\n", @grabArray;

__DATA__

  Grab this 'test1' (repeat/new)
many lines
  Grab this 'test2' (repeat/new)
many lines
  Grab this 'test3' (repeat/new)

##</code><code>##

test1
test2
test3