$s = 'aaaabaaaabaaaaabaaaab';;

$s =~ /^((.*).*)\2$/ and print "$1/$2";;
aaaabaaaaba/aaaabaaaab

##</code><code>##

$s =~ /^((.*).*)\1*\2$/ and print "$1/$2";;
aaaabaaaaba/aaaabaaaab

##</code><code>##

$s = 'aaaabaaaabaaaaabaaaabaaaaabaaaab';;

$s =~ /^((.*).*)\1*\2$/ and print "$1/$2";;
aaaabaaaabaaaaabaaaaba/aaaabaaaab