Untested, and not very thought out:
$_ = "hellohiworldhellohiworldhellohiworldhellohiworld";
if (/^((.+?)\2+)$/) {
print "[$1][$2]\n";
}
Update: Hmm, this does not work, and I'm not sure why (regex bug? or bad code?) :-(
Ok, got the above code to work at least the way I was expecting, but still probably not what you want.
<update>Though here's something that seems to do what you want:
use warnings;
use strict;
$_ = "helloworldhellohellohihellohiworld";
my %pttrns;
PTTRN: {
if (/\G(.{2,})(?=.*?\1)/g) {
$pttrns{$1}++;
SKIP: {
my $again;
for my $pat (keys %pttrns) {
if (substr($_, pos, length $pat) eq $pat) {
pos() += length($pat);
redo SKIP;
}
}
}
redo PTTRN;
}
}
print "[$_]\n" for keys %pttrns;
~/tmp >./tst
[world]
[hello]
[hi]