It sounds like you are asking for a recursive grep. Fortunately the gnu egrep already has a recursive switch (-r -- see the manpage). If you really wish to do this from Perl, then you'll find the module File::Find useful. For example:

use File::Find;

find(\&wanted, @directories_to_search);

# untested
sub wanted {
  return unless -f $File::Find::name;

  my $f;
  unless ( open $f, '<', $File::Find::name ) {
    warn "couldn't open $File::Find::name: $!\n";
    return;
  }
  my $matched;
  while (<$f>) {
    $matched = 1 if /word_to_look_for/;
  }
  print "found word_to_look_for in $File::Find::name\n"
    if $matched;

}
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