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 =~ $_
� }