Missing semicolons aside, it might read more clearly as:

my $file = "...";
unless( open( FILE, "<", $file ) ) {
  print STDERR "Error opening '$file': $!\n"
  print STDERR "Hit <ENTER> to exit\n";
  scalar <STDIN>;
  exit 1;
}
my @array = <FILE>;
close( FILE ) or die "close '$file': $!\n";
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