use warnings;
use strict;

my $words = 'xxxhexxxxxxxx xle xxnxle nxxx xxnxxx xnxxhexx nxxxxx xlexxxxxx nxnx xxxx';
my $string='helen';
print "string=$string\n";
print "words=$words\n";

my @other_stuff = split (/\s+/, $words);
my @pairs = $string =~ /..?/sg;

my $target=$pairs[0];
my $idx=0;
while ($words =~ /(\b\w*?$target\w*?\b)/g ){
    print "target=$target,matched=$1\n";
    $idx++;
    $idx=0 if $idx > $#pairs;
    $target = $pairs[$idx];
}