#!/usr/bin/perl -wl
use strict;

sub msplit {
    my ($delim, $str) = @_;
    my $pat;
### $pat = q/ (?> (.*?) (??{ shift @$delim }) (??{ $pat }) )? /; ### UPDATE: WRONG
    $pat = q/ (?> (.*?) $$delim[0] (??{ shift @$delim; $pat }) )? /;
    $str =~ /^ $pat (.+) /x;
}

print for map "'$_'", msplit [qw(: :: \s+)], "a:b::c  d";