#! perl -slw
use strict;

# my %hash = ...;
my $str = 'Hi this is the sample string for string search';
my @words = split ' ', $str;

for my $start ( 0 .. $#words - 1 ) {
    for my $end ( $start .. $#words ) {
        print "Lookup: ", join ' ', @words[ $start .. $end ];
    }
}

__END__
C:\test>1001794
Lookup: Hi
Lookup: Hi this
Lookup: Hi this is
Lookup: Hi this is the
Lookup: Hi this is the sample
Lookup: Hi this is the sample string
Lookup: Hi this is the sample string for
Lookup: Hi this is the sample string for string
Lookup: Hi this is the sample string for string search
Lookup: this
Lookup: this is
Lookup: this is the
Lookup: this is the sample
Lookup: this is the sample string
Lookup: this is the sample string for
Lookup: this is the sample string for string
Lookup: this is the sample string for string search
Lookup: is
Lookup: is the
Lookup: is the sample
Lookup: is the sample string
Lookup: is the sample string for
Lookup: is the sample string for string
Lookup: is the sample string for string search
Lookup: the
Lookup: the sample
Lookup: the sample string
Lookup: the sample string for
Lookup: the sample string for string
Lookup: the sample string for string search
Lookup: sample
Lookup: sample string
Lookup: sample string for
Lookup: sample string for string
Lookup: sample string for string search
Lookup: string
Lookup: string for
Lookup: string for string
Lookup: string for string search
Lookup: for
Lookup: for string
Lookup: for string search
Lookup: string
Lookup: string search