Roboticus@Roboticus-PC ~
$ cat regex_alt.pl
use strict;
use warnings;
my $text=<<EOT;
Now is the time for all good men to come to the aid of their party.
EOT

print "ORDER MATTERS FOR COLLISIONS:\n";
while ($text=~/(the|their)/g) {
        print "\tfound $1 at $-[0], $+[0].\n";
}
print "VS:\n";
while ($text=~/(their|the)/g) {
        print "\tfound $1 at $-[0], $+[0].\n";
}

Roboticus@Roboticus-PC ~
$ perl regex_alt.pl
ORDER MATTERS FOR COLLISIONS:
        found the at 7, 10.
        found the at 44, 47.
        found the at 55, 58.
VS:
        found the at 7, 10.
        found the at 44, 47.
        found their at 55, 60.