#!/usr/bin/perl -w
use strict;
my ($wholefile);
my (@keys, %SUBS);
$SUBS{'b'} = 1;
$SUBS{'c'} = 1;
local $/;
open(H,qq|$ARGV[0]|) or die "USAGE: wierd2.pl <filename>"; #sloppy example
$wholefile .= <H>;
close(H);
foreach (keys %SUBS) {
    while($wholefile=~m/\b$_\b/g){
	push @keys, $_;
    }
}
1;