#!/bin/perl -w
$names++, shift if $ARGV[0] eq "-l";
$search = shift;
$showname = @ARGV > 1;
@ARGV = "-" unless @ARGV;
@ARGV = grep { -T or $_ eq "-" } @ARGV;
exit 0 unless @ARGV;
while (<>) {
        next unless /$search/o;
        if ($names) {
                print "$ARGV\n";
                close ARGV;
        } else {
                print "$ARGV: " if $showname;
                print;
        }
}

##</code><code>##

1.  grep pattern /tmp/file
2.  cat /tmp/file | grep pattern