use Perl

Usage: ack [OPTION]... PATTERN [FILES]
Search for PATTERN in each source file in the tree from cwd on down.
If [FILES] is specified, then only those files/directories are checked.
ack may also search STDIN, but only if no FILES are specified, or if
one of FILES is "-".

Default switches may be specified in ACK_SWITCHES environment variable.

Example: ack -i select

Searching:
    -i              ignore case distinctions
    -v              invert match: select non-matching lines
    -w              force PATTERN to match only whole words

Search output:
    -l              only print filenames containing matches
    -o              show only the part of a line matching PATTERN
                    (turns off text highlighting)
    --output=expr   output the evaluation of expr for each line
                    (turns off text highlighting)
    -m=NUM          stop after NUM matches
    -H              print the filename for each match
    -h              suppress the prefixing filename on output
    -c, --count     show number of lines matching per file

    --group         group matches by file name.
                    (default: on when used interactively)
    --nogroup       One result per line, including filename, like grep
                    (default: on when the output is redirected)

    --[no]color     highlight the matching text (default: on unless
                    output is redirected, or on Windows)

File finding:
    -f              only print the files found, without searching.
                    The PATTERN must not be specified.

File inclusion/exclusion:
    -n              No descending into subdirectories
    -a, --all       All files, regardless of extension (but still skips
                    blib, CVS, RCS, SCCS, .svn and _darcs dirs)
    --[no]asm       .s and .S
    --[no]binary    Binary files, as defined by Perl's -B op (default: off)
    --[no]cc        .c and .h
    --[no]css       .css
    --[no]elisp     .el
    --[no]haskell   .hs and .lhs
    --[no]html      .htm, .html and .shtml
    --[no]js        .js
    --[no]lisp      .lisp
    --[no]ocaml     .ml and .mli
    --[no]parrot    .pir, .pasm, .pmc, .ops, .pod, .pg and .tg
    --[no]perl      .pl, .pm, .pod, .tt, .ttml and .t
    --[no]php       .php, .phpt, .htm and .html
    --[no]python    .py
    --[no]ruby      .rb, .rhtml and .rjs
    --[no]scheme    .scm
    --[no]shell     .sh, .bash, .csh, .ksh and .zsh
    --[no]sql       .sql and .ctl
    --[no]tt        .tt and .tt2
    --[no]vim       .vim
    --[no]yaml      .yaml and .yml

Miscellaneous:
    --help          this help
    --version       display version
    --thpppt        Bill the Cat

GOTCHAS:
Note that FILES must still match valid selection rules.  For example,

    ack something --perl foo.rb

will search nothing, because foo.rb is a Ruby file.