If I am not mistaken, this can be rewritten as:

#!/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 exa
+mple
$wholefile .= <H>;
close(H);
foreach (keys %SUBS) {
    while($wholefile=~m/\b$_\b/g){
    push @keys, $_;
    }
}
1;
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Of course, I have no idea how:

You are getting the %SUBS hash populated in the first place. I thought that was the purpose of the script?

Why you would want to do this

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