#!/usr/bin/perl -w
use strict;
use warnings;

my %lookingFor = (
        'lazy'  =>      ['lazy', 'tired'],
        'entry' =>      ['entry', 'opening', 'ingress'],
        'file'  =>      ['file', 'files', 'filehandle'],
        'such'  =>      ['such']
);

# Build an inverted hash with pointers from the individual items
# to the matching key in lookingFor
my %revLUP;
for my $k (%lookingFor) {
        for my $v (@{$lookingFor{$k}}) {
                $revLUP{$v}=$k;
        }
}

while (my $buf = <DATA>) {

        # Print line if it has a 'magic word' in it
        print $buf      if      grep { defined $revLUP{$_} }
                                split /\s+/, $buf;
}
__DATA__
Now is the time for all good men to come to the
aid of their party.  The quick red fox jumped
over the lazy brown dog.
[tye]: yes, on Window or on Unix,
the old file is still open so it is just
its directory entry that gets clobbered
[bart]: On Linux, you can unlink a
file and the processes that have the
file open, will still see the contents. I
suspect the same happens here.
[tye]: "busy" only seems to apply to
executable files, talexb. no problem
deleting files that are open (though
Win32 C RTL /defaults/ to locking
the file such that this is prevented)
[blokhead]: in short, the filehandle
is tied to an inode, not a filename
[bart]: Meaning, the directory points
to the new contents, and the old
contents is unlinked (but visible). Is
that correct?