use strict;
use warnings;

my $str = "x\nab\ny";
my $re = '^ab$';
    
print $str =~ /$re/ ? 1 : 0, "\n";    # 0
print $str =~ /$re/m ? 1 : 0, "\n";   # 1
    
my $qre = qr/^ab$/;
print $str =~ /$qre/ ? 1 : 0, "\n";   # 0
print $str =~ /$qre/m ? 1 : 0, "\n";  # 0  but I think 5.8.x still had this as 1