use strict;
use warnings;
use Data::Dump;

my @var1 = ('gugu', 'gugus', 'and gugut for','gugas and', 'gurit for','granit')
;
my @var2 = ('gugi', 'gugis', 'and gugit for','gugas and', 'gurit for','granit')
;
my ($ret, $match);

print ("get any string 'gu' not followed by 'gu'\n");
foreach (@var1) {
    $ret = $_ =~ /gu(?!gu)/p;
    $match = $ret eq 1 ? 'found' : 'nomatch';
    print "<$_> $match ";
    dd ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH};
}
print ("\nget any string 'gu' followed by 'gi'\n");
foreach (@var2) {
    $ret = $_ =~ /gu(?!gi)/p;
    $match = $ret eq 1 ? 'found' : 'nomatch';
    print "<$_> $match ";
    dd ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH};
}