That code doesn't compile. TEST starts with double quotes and ends with a single quote. If I fix that, this works as expected for me. Here's a version you can run with your $x argument given on the command line:

use strict;

my $x = shift(@ARGV);

my $a = "TEST";
  if ($x == 1) {
    $a = "one";
  } elsif ($x == 2) {
    $a = "TWO";
  } else {
    $a = "EMPTY";
  }

print "a=$a\n";
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