What is qr for in reg expressions in a a string?

[Motherofperls]

I've been reading the previous post and was wondering about what qr does in 
this code.

use strict;
  use warnings;

  my @array = (
    qr'^to: myprog'mi,
    qr'^from: [EMAIL PROTECTED]'mi
  );

  my $str = 'To: myprog with trailing text';

  foreach (@array) {
    print "found\n" if $str =~ $_
  }