find path -type f -print0 | xargs -0 grep -i -n pattern

##</code><code>##

    path/filename:line#:content of line containing pattern
    path/subdir/filename:line#:another line with pattern in it

##</code><code>##

#!/usr/bin/perl

use strict;
# use Data::Dumper;   # you might want this

die "Usage:  $0  search_path  search_pattern\n"
   unless ( @ARGV == 2 and -d $ARGV[0] );

my ( $path, $pattern ) = @ARGV;
my @filelist;

open( my $find, "-|", "find $path -type f -depth -print0" )
    or die "Unable to run 'find $path ...'\n";
{
    local $/ = chr(0);  # set input record separator to null byte
    @filelist = <$find>;
    chomp @filelist;  # remove null byte terminations
}
close $find;

my %found;
for my $filename ( @filelist ) {
    #  $. = 0;  # (update: this line is not needed)
    open( my $fh, $filename );
    while (<$fh>) {
        $found{$filename}{$.} = $_ if ( /$pattern/ );
    }
    close $fh;
}

# check out how the data is stored if you want:
# print Dumper( \%found );

# or pretty-print it:
for my $file ( sort keys %found ) {
    # parse $file into directory and filename if you want
    for my $line ( sort {$a<=>$b} keys %{$found{$file}} ) {
        printf( "File <<%s>> LineNo <<%d>> matches: %s",
                $file, $line, $found{$file}{$line} );
    }
}