If you go over the entire list for every word, it's just going to take a lot of time. You want a hash instead.

#!/usr/bin/perl

use strict;
use warnings;

# the diamond operator is special:
# supply filenames on commandline or provide input on STDIN and it jus
+t works

my @word = <>;
chomp @word;

my %in_list;
undef @in_list{ @word }; # now all entries from @word are keys in %in_
+list

for( @word ) {
    my @hook = grep { exists $in_list{ $_ } } (
        substr( $_, 1 ),
        substr( $_, 0, length( $_ ) - 1 ),
    );
    print "$_: @hook\n" if @hook;
}
[download]

You go through the list of words, generating front and tail hooks for each, and then look up whether there such a key exists in the hash.